Why the code color different to normal C# project? How to fix it?

The method name of class should be light yellow or yellow, but in Unity project it is blue (same as C# keywords). Both left and right project use same IDE VS2022, and same Editor Color Scheme: Visual Studio 2019, which located at menu tools → options → editor → advanced → Editor Color Scheme.

I’d say that it’s the Unity plugin that is installed into your IDE that causes Unity event methods to be colored differently. Try that in Unity project (on the left), create a method with a custom name.