Why do some people need low-contrast themes?

Everyone is familiar with the high-contrast themes that are created for people with poor eye-sight. Because of the high contrast it is easier to see what is on the screen.

However, I heard there are also low-contrast themes. Could someone give some examples, but most importantly, could someone explain why there are low-contrast themes and who are helped by it?

I have had to install a (Windows) PC for somebody who needed low contrast themes in a previous job. This woman could only see "light" and no colours, and had low vision in general. (I think she said she had no cone cells or something like that, but it's been 2 years). She used a low contrast theme in Windows that used 2 shades of blue.

She described looking at a screen with high contrast (e.g. black on white or white on black text) as "looking straight into a spotlight and trying to see/read something that's written on it".

At least one other almost blind person told me it was the same or similar for him (but his eyesight is so bad now that he does everything with a braille reader & TTS anyway—he also uses the console most of the time).

BTW: I think it's possible to use compiz filters to show "low contrast" & "high contrast" versions of a normal display, but I don't know how well that works in practice?

In an attempt to answer your question, low-contrast themes have the advantage of being simpler and cleaner. Even though its harder to identify what's on the screen, some people find that low contrast themes are less shocking than high contrast ones.

I find low contrast themes useful when using the computer in a dark room, for example, because I don't have light reflecting on the screen. I hope it answers at least part of the question.