I am pretty sure that you can’t find a place where you can just input your own colours into the scene mesh. You need to build this functionality. I might be wrong but this is how I see it.
I think like @jim_selikoff said earlier you would need to replace this function with your own…
…to draw the whole mesh again on the scene but like the example scanner project states this would a lot slower process.
/** Render the scene mesh from the given viewpoint.
A virtual camera with the given projection and pose matrices will be used to render the mesh using OpenGL. This method is generally faster than using sceneMeshRef and manually rendering it, since in most cases STScene can reuse mesh data previously uploaded to the GPU.
**@param** cameraPose A GLKMatrix4 camera position used for rendering.
**@param** glProjection Projection matrix used during rendering. See also [STDepthFrame glProjectionMatrix] and [STColorFrame glProjectionMatrix].
**@param** alpha A float value for transparency between 0 (fully transparent) and 1 (fully opaque)
**@param** highlightOutOfRangeDepth Whether the areas of the mesh which are below Structure Sensor minimal depth range should be highlighted in red.
**@param** wireframe Whether to render a wireframe of the mesh or filled polygons. When enabled, STMapper needs to be initialized with the `kSTMapperEnableLiveWireFrameKey` option set to `@YES`.
**@return** TRUE on success, FALSE if there is no STMapper attached to the same STScene with the corresponding (wireframe or triangles) live mode enabled.
Hopefully I am not driving you to a full desperation.