Change colours of Code

I want to change the colour of some important variables in my code. My code is quite long and sometimes I have to change these specific variables, but it is quite annoying to search them, beacause their is no contrast and it is hard to find them. Is their a possibility to change their colour?

SetOptions[$FrontEndSession, AutoStyleOptions -> {"SymbolContextStyles" -> {"highlight" -> Green}}] AppendTo[$ContextPath, "highlight"];

and before those important variables (symbols) appear for the first time, tell Mathematica to add them to the highlight context (e.g. var1 and var2). They will be green everywhere.
highlightvar1;