With only the safe lights on or with the room fairly dark place a negative in the carrier and a white sheet of paper on the easel. Open up the lens all the way and turn the enlarger light on. Set the head height to about an 8X10 enlargement. Set all 3 colors to 0. The Cyan should stay at 0 for the test. Now slowly rotate the magenta to a higher number. You should see the image get redder (pinker) and darker as you rotate to the highest number (170-200) Set the Magenta to 0 and do the same exercise with the yellow filter. As you go higher it should both a deeper yellow and darker. If you don't see a major change from 0 to 170 then the filters may be faded or need some kind of adjustment.