The "color blind test" was used a lot during the time that I was diagnosed. Not the primary diagnosing tool, but it was considered significant by an opthalmologist I went to for glasses.
He found that I had nearly total color blindness on his test. (I didn't notice the color blindedness in real life because most colors in the world are actually stronger and more discrete than those on the test. And actually I was used to not seeing bright colors as bright.) He said that this was significant for MS. (I had not yet been dx'd with MS and was not dx'd until I had an MRI and VER later). I asked him specifically what his test indicated for me and he said it was possible MS.

I think my color blindedness receded over the years. Because I think I do see colors well now. It's subjective, though.

My eyes have gone through many changes. They were nearly perfect during the long period after the ON cleared up completely. The smoke from a forest fire damaged them, and this damage was repeated ten years later in another forest fire, but I mostly recovered from these assaults. During the fires and afterwards for a few months I had periods of near blindness when my eyes went into spasm.