The Dyslexia Research Trust has a good article that picks out the yellow and blue filters as being particularly effective.
We believe in these visually calming & contrasting boards because the alternative is backing paper that you can't annotate on or keep refreshed with learning resources. In little or no time the traditional board looks shabby, unloved & far from achieving that accessibility goal you originally set out with.
Time is precious & accessibility/inclusion is a priority so how about maybe ticking off two BIG goals in one? ✅
Pick a pastel colour, size & orientation.