kohend
commented
2 years ago Thanks for the input, when designing that, I believed the different intensity would suffice as an indication, but it seems I was wrong, I'll think what can be done within the framework and visual constraints. I'm the developer of that game.
the only visual indication of the player's coloring of cells conflicting with a clue (number in a cell) is that the text color of the clue numeral changes from black to red.
especially in the case of a cell colored with white background, this { red text vs black text } is difficult for people with red-green color vision abnormalities to see. the red and green cone pigments being on the X chromosome, this sort of color-vision abnormality affects around 8% of males, a large fraction of the user base.
myself, having the mildest and most common sort of color-vision abnormality, "deuteranomaly" (mutated green-cone pigment), i can discern the red from black on white background if i'm looking right at it, but it doesn't stand out enough to reliably draw my visual attention (which i suppose the red color is intended to do). this morning i had to hunt brute-force across the board, somewhat incredulous that the status text at the bottom of the board said "Clues left: 1", and it took me a while to find the red numeral among a field of black numerals.
i would suggest visually indicating errored clue cells in a way that doesn't rely on hue. the idea that comes to my mind is to draw an additional / thicker inset border within these cells. it could even be a red border, which would signal to those able to see the color while the non-color distinctiveness of the thicker border would be readily apparent even to the color-blind.
perhaps testing the app in a grayscale display mode would give a clear idea of how effective a given visual presentation would be to color-blind people.