This seems a little subjective because you're relying on individual users to be able to distinguish between all of these colours, even though yellow and orange may not necessarily be of a sufficient contrast ratio for this to be possible.

Sorry for the confusion by highlighted cell I mean the one the user is currently on so if you could move around using arrow keys only one cell would be highlighted at a time. I'll have to try with Black and yellow, I originally planned on using something like bright orange with black letter and also separating the boxes using black. As far as the "unknown" squares I was going to use white but maybe a light red would help distinguish between them. for the highlight, I wanted to try and stick with another brighter color since navy would have my text color black disappear into it but if I went with your idea of having yellow text it would stand out much better.

I suppose what this comes down to more now is if it would be better or preferred to have bright color backgrounds with dark insides or dark backgrounds with brighter values within each box.

Thanks so much!

I was more curious about whether there were specific colors that are easier to see and or if there's a general color scheme that gets used. I was planning on using a bright orange with black text for a filled box, white for empty boxes and a lighter but bright blue for a highlighted box. I did check that the colors were acceptable together to the best of my ability as well. thanks for the response!