If you spend hours a day looking at the charts, then black or gray are easier to look at. Keep all indis a dull color unless you really like hot pink or yellow :-)
Try white exclusively for 1 week then switch to black or gray. You'll notice the difference.
When choosing the color scheme for your charts, 2 things are important. 1) It has to be easy on your eyes. Face it you have to look at it up to 24 hours a day as forex is traded around the world non-stop for 5 1/2 days a week. 2) Everything has to stand out so you can spot the emerging patterns and formations easily and fast.
Personally, I find black background with the traditional green/red candle combo is the best. I find the black background is easier on the eyes as with white background, sometimes you can get awful glare from the surrounding light or the sun and it can really strain your eyes when you've stared at it for a long time. Also with the black background, everything also stands out more and you also have wider choices of colors that you can use for indicators, lines and etc. on your chart as with lighter background, many colors don't stand out well.