Notification Colors

That red (#FF3B30) circle became one of the most anxiety-inducing design elements in history. Red triggers urgency. The white number creates contrast. It was behavioral engineering.

Facebook's blue dot (#1877F2) is subtler than red. It signals curiosity rather than emergency. "Something happened." Subtly powerful, driving engagement without immediate stress.

The double blue checks (or green in some contexts). Originally grey, turning blue when read. The ultimate social pressure—knowing they saw it and didn't reply.