Currently, the toolbar icons work well on dark backgrounds:
But on light backgrounds they become hard to read:
Since the toolbar icons are vectors, stored as meshes with materials, we could actually make the colors themable.
Each color is stored as a separate material, such as theme.general.base (white), theme.mesh.add (green), theme.mesh.modify (purple), theme.mesh.remove (Red) etc.
We could simply let the theme set these colors, so that bright themes can set the base color to be dark.