Is it possible to use a colour variable with functions

Yes, in OS7 you can set any of the style arguments for a style or using in your config. But you need to use Rgb16 values for each color you want to edit in the correct order and “~” for a value that is missing or should use the default.

The correct syntax would be (based on your using function):

StylePtr<crystal>("65535,0,0 ~ ~ ~ "),

See discussion here:

Style argument info here:

This will be coming to the Config Helper tool as well, more explanation and demo here: