What editors like VSCode do instead is to highlight the matching parenthesis when the cursor is over the other. That way you don't have to hunt for a matching color.
And to make any unmatched opening/closing parenthesis bright red. The invalid state is made very clear.
Together, these are much more effective.
I would actually prefer the opposite. Render the () characters as different matching glyph pairs. The space for distinctive asymmetric glyphs is a lot larger and not generally very loaded because people code 99.9% in ascii.
Interesting. But how many matching glyph pairs do we actually have in current fonts?
since it take me effort to actually parse the colors, this is a constant distraction.
so I can read monochrome text just fine, but multi-colored text really slows me down.
I can't tell some apart, but because they've got a different colour in-between, it makes it easier to jump between start and end of expressions. Being able to box blocks in my head faster.
That being said, I always have to tweak accessibility settings anyway. Change of font, change of size. Having to toggle off rainbow as well doesn't seem to really add to the large list of things.
Panic's "Nova" does this. It lets you pick your palette for the parenthesis from about 30 choices. It also adds vertical lines along the left edge to show indentation level and lets you choose from the same palettes. There's three at the bottom of both palette lists designed for protanopia/deuteranopia/tritanopia.