A lot of purple, oddly. A bit of blackness in the background that’s covered by static and a white-ish grey blanket if the eyes get stimulated enough. Sprinkle in some dull sparkles and a variety of flashes, now you have a vague sense of my internal vision
-edit: spelling

Why do you ask? Are you going through this yourself?

Completely blind in left eye from birth. In my right eye, white and cloudy, with a black ring around my eye. I can see some shadows and movement, a bit of contrast, occasionally light, but no colour. I sometimes get twinkling lights and random bits of colour (mainly red).

Here's me explaining what I see:

https://youtu.be/I3H76gv-QaA

There are many parts to the eyes and many reasons for why someone is blind. The cortex which is in the back of the eye processes what the eye sees. If the eyes can't see, the cortex could design random visuals.

How do these people answer this question?

Edit: guys my partner has been diagnosed with retinitis, im asking so we can prepare for the future, not to be funny. But thanks for the downvotes anyway