Terminals reliably recognize the 8 basic ANSI colors. There are also bright versions of each of these colors that you can use, but less reliably.
Things to note
Background color is available but we haven’t taken advantage of it yet.
Some terminals do not reliably support 256-color escape sequences.
Users can customize how their terminal displays the 8 basic colors, but that’s opt-in (for example, the user knows they’re making their greens not green).
Only use color to enhance meaning, not to communicate meaning.