I sometimes use a dark brown pair of prescription sunglasses and they really do help. I think the reduced light is one reason but another reason seems to be the bigger lenses which mean I don’t get a lot of unfocussed vision as I would do with my normal glasses. I sometimes wear them on cloudy days and also indoors.
In addition to helping with Visual Vertigo, tinted glasses are said to help with migraine and epilepsy.
I get the impression that the exact choice of colour varies from person to person but I imagine (justguessing) that colour is not a great deal. Some specialist opticians use “colorimetry” to help match the right colour tint to you but this is relatively expensive. (A few hundred pounds here in the UK.)
Take a look at the VV case described on this page. Visual Vertigo Syndrome (Journal Article Review) | The VisionHelp Blog
I also notice Scott has posted about when he was suggested to try green glasses!
-Wexan