It works as any other calculation. Can you explain what you need and we can help you formulate the syntax? :-)
ADDED: Conditional format simply needs a boolean true or 1 to evaluate so the calculation just needs to evaluate also to true.
I have a field which changes colour according to a batch number field 'colour fill' field. The fields only purpose is to change colour according to which number is entered in the job batch field. The 'colour fill' field appears on several layouts, and so when I need to amend the colour of the batch or add a new condition I have to do this across several layouts.
I wondered if it was possible to have the conditions placed in one place e.g. a field specifically to hold the conditions from which the 'colour fill' field could source for the conditional formatting? That way I would only have to amend the conditions one time.
I hope that makes sense, I have uploaded a screen shot of the current conditional formatting I have in place for the 'colour fill' field.
I nice idea, but not possible. You can, however, update it on one layout and then copy/paste the field to all your other layouts to save some time.
And you could go "old school" and set up a calculation field that selects "container" as the result type that returns different graphics (can be simple colored rectangles) based on the value of the Job batch field. The calculation would select either a related record with a container field or the repetition of a repeating container field in order to select a particular color. Thus you could update the calculation or the repeating field/set of related records one time and the change would apply to all layouts that used that calculation field to show a color.
And I've recently come across an idea where a web viewer is used to show a color specified as an RGB value: RGB values to Background color