My advice is to forget about using the colour head and stick to graded filters under white light. It can be a recipe for madness trying to find the right balance and when I tried I wasted many, many sheets of paper in the process. The simple theory for graded filters is "time for the whites, filters for the blacks". i.e. once you find the right times for highlights you shouldn't have to adjust that time as you go up the grades to grade 3 1/2 to drive more contrast. The trouble with colour heads in my experience is you also have to worry out times and so it's like starting all over again every time you want to change contrast. The fewer the variables the easier to make a satisfying print.