I’ve found in the past with complex calculations, and both Conditional Formatting, or display calculations, or workflow rules I try to work out the calculation in a calculated field first.  So I end up with a field that is something like “FieldXYZ_DisplayCondition”  - and I try to have the output of that as a simple number, like 1, 2, 3  which I map to the colour when I do the conditional formatting.

eg. in the conditional formatting logic it might be: 

if FieldXYZ_DisplayCondition = 1 then colour = green, if 2 colour = amber, else red.

If you do it this way - and you want to make a change to conditional formatting ANYWHERE in the system, then you only have to change ONE formula in the calculated field, and ALL the conditional formatting in all the views will change.

In this specific example though - you’ve talked about a value based on User?  Is the target and billability both based on the User object?  That might still be able to work - but I’m not sure there’s a “currently logged in user” ability in calculated fields to pick up whoever is logged in if that’s what you need to do?