I think it's because 'scratch3' has a ':: extension' category setting, whereas the default ('snap') doesn't.
hi:: extension
hi:: extension
And I haven't dug deep into Snapblocks, so correct me if I'm wrong, but I believe that the Scratch 3 extension blocks are using the ':: extension' category as a fallback, but that doesn't exist in the 'snap' style, so the color sets it to an empty value.
Oh yeah, you're right. When I did implement the snap style, I did include the extension color, but when I redid how category colors work, I removed it, but forgot to change the code that sets it to the "extension" category to instead set it to the "other" category.
god sends a message from the beginning
(original: wow, this is interesting. so you are telling me i can type this in and it becomes unrecognizable?)
edit: wait what this feels a bit creepy