A colour map is a second image that tags every element in a view with its own flat colour — one colour for the floor, another for each window, another for a mullion. It is never shown to you directly. It exists so the app can answer a single question: which element did I just click?

With a colour map attached, the mask tools gain click-to-select: click a wall and its exact silhouette becomes the mask region, hover and the element under the cursor highlights. No painting, no tracing around window frames.

It works on any image, not just CAD

A Revit import can bring its colour map with it, and that is the easiest way to get one. But you can upload a colour map to any image layer — a hand-drawn plan, a diagram, a render you colour-blocked yourself. The moment a layer has one, the segmentation tool lights up in the mask toolbars and behaves exactly as it does for a CAD import.

Add, replace, remove

The colour-map control sits in the layer’s mask row in the layers panel. It shows whether the selected layer has a map, and opens the actions:

Upload / Replace — pick a PNG or BMP.
Download — get the map back as a PNG, exactly as stored.
Copy / Paste — copy the map from one layer and paste it onto another. Instant at any size: pasting points the second layer at the same map rather than duplicating it.
Remove — detaches the map from this layer only. Any other layer using the same map keeps working.

Layers inherit the map

Because a layer only points at its map, derived layers get it for free:

What you do	Does the new image have the map?
Duplicate or copy a layer	Yes
Generate from a layer	Yes — the result keeps the source’s map
File a CAD extraction	Yes, on the extracted layer
Merge two layers	Only if exactly one of them had a map
Text-to-image, plain upload, frame render	No

Merging is deliberately cautious: if both layers had a colour map, neither one describes the merged pixels any more, so the result starts empty.

File requirements

A colour map is a lookup table that happens to be stored as an image, so the file rules are stricter than for a normal upload — and breaking them fails silently, producing a map that looks fine but selects nonsense.

PNG or BMP only. JPEG is rejected. JPEG compression shifts colours slightly across each block, so one flat-coloured element arrives as hundreds of near-identical colours — and each becomes its own phantom element.
Never scale a colour map in another tool before uploading. Smooth (interpolated) resizing invents in-between colours along every boundary, ringing each element with a halo of false ones. The app never interpolates for the same reason.
If you pad it, pad with pure white. White is the background colour; any other fill parses as one enormous bogus element.

Different size is fine. A map at a different resolution to its image needs no preparation — the app maps between them as you hover and click, losslessly. Only a different aspect ratio is adjusted, by adding white padding until the shapes agree; the map’s own pixels are copied across untouched. You will see a warning when that happens, because a framing mismatch usually means the map came from a different view than the image.

Auto-repair for shattered maps

A material-ID pass out of a renderer often arrives with hundreds of thousands of near-unique colours instead of a few dozen flat ones — anti-aliasing, per-instance colour on scattered planting, and subtle gradients all conspire. Such a file used to be rejected outright.

On upload, the app now repairs it. It works out the map’s true palette and snaps every stray colour onto the nearest real entry. On a real 3000×2400 export this turned 304,064 colours into 16 elements, visually identical at full size.

Two things to know:

Repair is lossy, and it tells you how lossy. The notice reports what proportion of the map was reassigned — on that same file, about a quarter, almost all of it planting merged into its surroundings. Elements that were only ever a scatter of near-unique pixels do not survive as separately selectable things.
Your original is kept. The unrepaired file is archived alongside the repaired one, so nothing you supplied is lost.

Repair runs on upload only. A map a layer inherited is never rewritten, since that same map may be in use by layers in other workspaces.

Maps that are noisy all over

The repair above assumes each element is one flat colour and only the edges between them are messy. Some maps are not like that — an AI-generated map in particular, because an image model cannot paint a truly flat fill. Every area comes back very slightly speckled, far too faintly to see, but enough that no two neighbouring pixels are exactly the same colour.

Those files used to be turned away as photographs. They are now recognised and cleaned up too. On a real 4736×3584 example, 208,224 colours became 26 elements, with about 1% of the marked area genuinely merged away.

Two consequences worth knowing:

Smooth fades come back as bands. If your map has a floor or sky that fades gradually, there is no single flat colour for it to become, so it is split into a handful of stripes. Clicking picks one stripe, not the whole surface. Paint those areas one flat colour if you want them selectable as a unit.
Very thin lines may not survive. A hairline that is one pixel wide has no solid interior to be recognised by, so on a speckled map it is absorbed into whatever surrounds it.

A genuine photograph is still refused, which is deliberate — a photo can be forced into a handful of colours, but the result would be a posterised picture masquerading as a colour map rather than an honest “this will not work”.

Generate a colour map

If a layer has no colour map, you can have one made for it: open the colour-map control and choose Generate with AI. The image is sent to GPT Image 2, which repaints it as flat colour-per-object, and the result is filed onto the layer automatically — including the clean-up described above, which a generated map always needs.

It works from a fixed set of categories — sky, water, vegetation, terrain, road, facade, glazing, door, roof, interior surfaces, structure, railings, furniture, people, vehicles, and a catch-all for anything else. Each always gets the same colour, so maps generated for different images stay comparable, and you can tell at a glance what the model decided something was.

It uses credits, at the same rate as any other generation on that model. GPT Image is not a Google model, so on a Studio pilot it draws on the paid-model budget rather than being unlimited, and it is not available on the Blueprint tier.
It can take up to 2 minutes. The control spins and stays locked until it finishes; you can close the panel and keep working.
With a map already in place the action becomes Regenerate with AI, which replaces it. The previous map’s file is not deleted — other layers may be pointing at it.
It reads what you see: if the layer is cropped, the map is generated from the cropped image.

You can also start it from the mask tools. The segment icon is now shown even when a layer has no colour map: press it and you are asked whether to generate one, with a reminder that it uses credits. Say yes and you stay exactly where you are — the icon turns into a spinner while it works, and becomes the segment tool once the map is ready. You can leave the mask tools and come back; the generation keeps running and the map appears on the layer when it finishes.

It is a starting point rather than a precise instrument. A model decides for itself what counts as an object, so expect to check the result — and for a CAD view, an exported material-ID pass will always beat a generated one.

If click-to-select behaves oddly

Everything selects as one huge region — the map probably has a transparent background instead of a white one.
Clicking selects a sliver, or nothing — the map was likely saved as a JPEG at some point in its life, or resized with smoothing. Re-export it as a PNG at its original size.
The wrong element highlights — the map and the image are probably from different views. Check whether you saw a framing warning when it was uploaded.

Mask & inpaint — use click-to-select to pick the region to regenerate.
Layer masks — the mask a selected element becomes.
Import from CAD — Revit views arrive with a colour map.
Images & layers — the layer a colour map is attached to.