I have a Kobo Clara Color. I like the product but colors are mostly a gimmick. Useful for the occasional chart and for books cover and that’s pretty much it.
Don’t expect iPad quality color, they’re very washed out.
I think a dedicated e-reader is a great choice (I only read books, not comics or other graphics heavy documents) but for that grayscale would be more than enough and color is an extra.
I would recommend you to go to a store and have a look live at a color eink screen to get a feel for what they offer.
My kids have Clara's and they love them for graphic novels. They had b/w kobo's before but would never go back (unless they stopped reading graphic novels).
I agree it's probably an unnecessary expense for 99% of people, but I actually find it very useful reading articles, news and academic work. Also, I really like the washed out newspaper look the colours have even though this makes them ill equipped for graphic novels.