I agree that an indication like you mention would be good.
I don't see a problem with using blue though, even if that's also used in the mod matrix mode, since these are distinct modes indicated by the lit up mode buttons at the top. Also, according to the manual you need to hold the "Patterns" or "Save" buttons to access the sequencer patterns. If that's the case, the colours shouldn't really matter since you'll be completely aware that you're accessing sequencer patterns.
Edit: When the Pattern/Save buttons are held, it would be useful if the linked-to pattern's button, if any, is lit in another colour (maybe it is(?), but the manual doesn't say).
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