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.
I have tried it before, unfortunately never found it that handy. For starters you need a pretty complicated expression not already disambiguated by layout to start to care. Which is the sort of thing people try to avoid anyways. Second, there are not a huge number of colors that are super distinct when not right up against each other, doubly so when you consider all of them must be very distinct from the background color. Lastly there's a lot of finickiness with other usages of colours conflicting.
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.
Because it doesn't work very well in practice. The parentheses are very small glyphs, so the colors are actually barely visible on them, unless you have an extremely thick font. And if you have an actually complex expression, it easily turns into color soup. If you really need a complex parenthesised expression, it's much better to use newlines and other means of spacially aligning the code, Lisp style, then having it all in one line with rainbow parens.
The built-in editor of Casio calculators is doing this, on some crappy 80x8 screen. I think this is not too uncommon. My editor only colours the parentheses that I currently edit, which I find much less intrusive and has the same (I would say a better) effect.
Terrible idea for color-blind people. And I don't even mean severely color-blind, like when you can't distiguish red from green at all, but something more common and less severe, like deuteranomaly - where it's shades of these colors that are hard to distinguish.
Because the rainbow parenthesis alternate in frequency of brightness, its actually really easy to distinguish which is which, unless you're severely colour blind.
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.
The color blind would still see the parenthesis at least like they see them currently without the color coding though, given they are distinguishable from the background by lightness.
Realistically, you're probably going to want to let the user choose the colors used for their parenthesis, and once you have that set up it's pretty easy to include one or more colorblind-friendly color schemes.
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.
Those people are able to distinguish suggested colors - the example is using primary colors. And at worst, it would be the same as all parenthesis being the same color (black).
no, its not. first of all either I sense brightness differently, or I use it to compensate. so highlighting of any kind make the text a mix of brightnesses from dingy to glaring across the text.
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.
