syntax definition problem

[Rich]

I am writing a syntax definition file for a smallworld *.magik file and am trying to get any word after a colon to be highlighted in red. In the following examples I need :argument3 in red -

(argument1, argument2, :argument3)
or
(:argument3, argument1)
or
{:argument3}

Is using wildcards for a set of keywords an option?
I'm using TextPad 4.4.
Any help would be much appreciated.

Thanks

Rich