in the options -> appearence I can change only 2 colors: silver & bluy. how can I extend this list ? May be to edit some .cfg files or edit registry entries ?
I am asking because in hightlight colors there is so nice orange color...
You can't. There are possible options for themes, but you can't extend the built-in colors. If you want themes, Google is your friend as I am not very familiar with theming in SL.