I was reading the instructions from Howie's site and this is what he says
Considerations for other supplies and materials
I suggest making the quilt out of two separate colors: a light color on top, and a dark color on bottom. This is not an asthetic suggestion, but one more in tune with performance. A light color will absorb less heat and therefore will loose less through heat radiation. Thus, it will hold more heat in the bag when used on top. Because dark colors absorb heat quickly, but also disperse it quickly, they are suited for use inside the quilt where the quilt can be turned inside out and dried out quicker in the backcountry. Also, when the user wishes to not be seen as easily, the darker color can serve as camouflage in the night. The breathability of a fabric is also vital. The human body emits nearly a pint of moisture every night during sleep. A fabric that is not breathable will trap this moisture, encouraging mildew and loss of loft. It is important to air out a sleeping bag every morning, in any case, to ensure complete dryness. A fabric that is too breathable, however, will let too much heat escape right through the individual threads and will hinder the bags performance. Use a lightweight down-proof breathable rip-stop nylon. A Durable Water Repellant (DWR) finish will make a limited amount of moisture (from the outside) bead up and roll off of the quilt, rather than soaking in. I suggest using an uncoated rip-stop nylon between 1.1oz and 1.3oz per square yard.
Yosemite Sam: Are you trying to make me look a fool?
Bugs: You don't need me to make you look like a fool.
Yosemite Sam: Yer deerrrnnn right I don't!