Are you saying such a plugin exists that only works with named colors?
That would seem like a... usability disaster.
Any accessibility tool for vision should operate at an OS level to map colors across everything. And even if you wanted a web-only tool, it would need to similarly operate across all colors -- whether hex codes or in images or SVG's. Very few sites use any named CSS colors at all except for "white" or "black".
There are lots of areas where it's important to keep accessibility in mind... but named CSS colors would not seem to be one of them.
For contrast, css can be quite effective. A brute force background black, text white, link yellow has served me very well. For color blindness correction an OS level filter is the way to go.
This would be true if the CSS color names were actually reasonable, but many of them are not.
One would be better off using the results [1] of Heer & Stone (2012) [2] (or a similar analysis) to assign names to sRGB colors. You end up with 33 unique names instead of more than 100, and the number of unique names can be reduced further by merging synonyms.
It doesn't matter what the names are, the point is you can have a plugin that changes one color to another based on their names and what you can see. The names are a much smaller search space than "all possible hex codes".
I'd argue that the 147 named CSS colors are still too many (but definitely better than the ~16.8 million sRGB colors). Regardless, since hex codes are used in practice, they would still need to be dealt with.
I feel pretty confident saying that is not a relevant use case.
I used to use a hand written user stylesheet for color accessibility and know various people using different tools to get the contrast they need. Named colors are not a factor.
I honestly don't know, it's just what I was told by someone who is visually impaired a long time ago. That it's easier if people use the names instead of the hex codes because then they can more easily convert that.
As others say, this sounds unlikely and unwieldy. It also doesn't quite make sense. How would it help to change "lightyellow" to "yellow", say, without knowing the contrast of the other colors next to it? Are you trying to darken it or lighten it?
It would make much more sense to do something check the lightness ratio between the foreground and background colors, and increase that ratio on the fly. Chrome can already tell you if the color ratio is too low to pass accessibility guidelines. There are a number of plugins that do this, like Color Enhancer [1] or High Contrast [2].
That would seem like a... usability disaster.
Any accessibility tool for vision should operate at an OS level to map colors across everything. And even if you wanted a web-only tool, it would need to similarly operate across all colors -- whether hex codes or in images or SVG's. Very few sites use any named CSS colors at all except for "white" or "black".
There are lots of areas where it's important to keep accessibility in mind... but named CSS colors would not seem to be one of them.