I see. I use the normal site on a phone with dark theme. Then this is an issue with the dark theme. The cards are slightly tinted differently but isn’t obvious at all that they are indicating color like in the light theme. I see it clearly in the light theme.
Maybe the style can be improved for the dark theme? Also, to me highlighting the whole card seems to hint who’s turn it is, not the color they are playing. I actually thought this was the case for a while.