Use your cpap machine when you have a cold if you possibly can. Raising the humidity a little will help with some congestion. A neti pot rinse or Saline Spray about a hour before bedtime will also help with congestion.
You may need to elevate the head of your bed just a few inches.
Some people find that a full face mask helps with congestion since you can breathe through your mouth as well with a full face mask.
If you absolutely cannot sleep with the machine, sleeping in a recliner will help.
I have used cpap for 7+ years and have had a few colds in that time! I have NEVER not used my cpap and, in addition, found that my congestion cleared with the cpap and a slightly higher humidity setting while I got through the cold.