In the latest Overwatch update, Blizzard added a little something that wasn’t in the patch notes. A subtle change to the game has foiled certain types of aimbots, rendering them useless.
Check out Overwatch patch 1.12 for all the changes, but not this one.
According to Redditor a16425, chatter on South Korean Overwatch forums suggests the bots it targets are called image-recognition-based bots, and they work by honing in on a specific hue - that of the lightly glowing outline that hovers around enemy silhouettes.
So the bots are programmed to see this colour and nudge the cheater's aim to where it is. The latest patch tweaks that outline to slightly change in colour throughout the match. It’s a small change that you won’t notice with the naked eye, but it’s enough to throw off the bots.
When reprogrammed to target the colour range, rather than a specific RGB value, those bots will have a much higher failure rate. It should deal quite the blow to cheaters.