How can I tell Xcode 4 what syntax coloring to use for a file type it doesn't (appear to) know?

I'm working with some OpenCL code in Xcode 4. I don't want to compile the code with Xcode - that's done dynamically by the C++ code. Xcode 4 doesn't know about OpenCL syntax coloring. How can 开发者_开发问答I tell it to apply C syntax coloring instead?

(It's not just for coloring. It also gets indenting wrong etc.)

xCode Menu [Editor]->[Syntax Coloring] doesnt work?