Syntax highlighting in rich text items isn't support (except for static highlighting when copying formatted RTF as quant described).
Another option is to import a source code file as a template in UR and use UR's text file syntax highlighting.
http://www.kinook.com/UltraRecall/Ma...itordialog.htm
After creating a text file template item, create new items from that template and copy/paste source code into it.