I am experimenting with a color font in COLR-CPAL format. Trying out if I can make an agrave as a composite from a and grave, the preview in the app looks OK.
When I generate a font and check it out, the agrave shows up wrong. When I open the TTF in a TTF editor, I can see the color layers appended as glyphs. The agrave shows up as 3 composites: agrave.layer0, agrave.layer1 and agrave.layer2. Unfortunately for all three the components are the normal a and grave, rather than the .layer0, layer1 and .layer3 glyphs. If I make a manual change of the composites everything shows up fine, so the references in the tables are OK.