See Ambiguous feature call - Whats wrong? - Designer, User or Bug? for a description of what the Ambiguous Feature Call error means.
See Type Conversions for a discussion of Types and how to convert from one type to another. There is a Color section.
In this particular case I think if you do one of the following it will work:
HSBType::RED as Command
HSBType::RED as Number
HSBType::RED.toString
This will help the Rules engine avoid the ambiguous method call.