My five-year-old daughter and I are always the first two up in our house and we start each day with a couple of rounds of her favorite game... Uno.
Unfortunately, my red-green color deficiency makes distinguishing between the yellow and green cards in this game a difficult task, especially in less than ideal lighting. In fact, my five-year-old daughter has already gotten in the habit of letting me know whether a card is yellow or green whenever the color changes (and I'm fairly certain she's telling me the truth... most of the time).
Two Minecraft Uno Five cards, one yellow and one green, showing a pixelated gray wolf in the middle of the card. On the right is a snip from the Colour Contrast Analyzer tool showing the hex codes for the shades of yellow and green pulled from the cards. The tool shows that the contrast ratio between these two colors is just 1.1:1.
The designers for this game could have simply made the green darker and the yellow brighter to avoid any contrast issues. This adjustment would have made the deck accessible for those with color defiency without having a negative impact on anyone.
Designing for accessibility is designing for everyone to have a universally positive experience... even if their kid laughs uncontrollably while stacking Draw Two cards on them).
Meme with two images. The first shows an Uno Wild card that reads "Make accessible decks or Draw 25". The second image shows a player, whose face has been replaced with an Uno logo, holding a handful of cards.
If you're designing a project and would like to know how your color contrast measures up to text and non-text accessibility standards, check out WebAIM's Contrast Checker.