Strange behaviour when outlining COLRv1 fonts
I have been running into some issues with COLRv1 fonts when turning them into outlines: The normal font renders as intended, when outlined some colours turn off one of the RGB channels (turning white to yellow). See the example in the screenshots where the white (circled) is turned into yellow. This is independent from the "yellow palette" of the letter, in other COLRv1 fonts white also turns into full RGB yellow.
See Nabla as an example:
https://fonts.google.com/specimen/Nabla
I don't believe this is caused by the "white" (as the error also turns, for instance, black into blue, removing a single RGB channel as well). I suspect it's converting the layers (of which the colorfont is constructed) in a faulty way.
This happens in Illustrator '26 (30.3 to 30.7), but I have also seen it happen in Illustrator '25, though only rarely. It doesn't happen in CMYK files: only RGB files and regardless of color space.
Noto Emoji also creates a lot of rendering bugs, but as I haven't created the font I don't know much of it's construction. But perhaps good to take along. This font also includes some gradients which are flattened to bitmaps in a RGB file. See the hat and hair of the 🏌️ emoji when outlined [ Golfer (U+1F3CC) ].
Typearture
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