keyword1 and keyword2 have the same color?

[ghost]

I have tried different color schemes. I found that keyword1 and keyword2 always have the same color. keyword3 is in different color. And if you set a keyword as keyword4 then it will become invisible. Please correct me if I'm wrong.

[SpartanJ]

Not always, the default color scheme does use different colors. I don't remember by memory each case but it's true that sometimes it's repeated. And there's not a particular rule on when to use keyword and keyword2, but keyword3 is always used for function parameters. You'll be required to have semantic-highlighting working with some LSP to be able to see it in use (any good LSP provides it, clang, or rust-analyzer or typescript-language-server). As for keyword4, it does not exist, editor currently supports 3 keywords, adding more is trivial but you need to add that color to each color-scheme and it's not that easy because not many support that many colors (currently most popular color-schemes provide a color palette that you need to follow, and the number of colors is limited).