Quiet, drab-colored UL pack?

I have a North Face Skareb 55. It just about fits the bill for all your stated requirements. 40lb. loads might be pushing it just a tad, if find the pack comfortable in the 35 lb. range. It’s just over 3300 c.i. at about 3 lbs. The pack is very durable, not at all noisy, and the streamlined shape is ideal for skiing, climbing, or any task that requires a full range of arm motion. The compression system (side compression straps and external shock-cord) works well for cinching the pack down tight. The pack has a hydration port and internal suspension for a bladder, but no separate pocket. Most folks use a pack liner, though, so that’s not a huge issue. Here’s a link:
http://www.thenorthface.com/opencms/opencms/tnf/gear.jsp?site=NA&model=AZJ8

GoLite offers the Gust in Black although it has hints of yellow. Granite Gear’s pack offerings are all available in darker colors.

ULA offers their bags in a Black and Green combo.

I can definatly sympathize with you on the color of equipment out there today. It seems like so much of it is in some bizzarre primary color combo, and it makes “stealth” trips very dificult.

Last year’s Phantom and Ghost packs were a nice brown/tan kinda color. Great suspension, light but not SUL (and arguably barely UL; under 3 lbs, IIRC), good packs, can frequntly be found cheaply. Some have mentioned stiching problems with the suspension, but I’ve not noticed any problems at all, and those that have have had their packs repaired/replaced by Mountainsmith. Campmor had ’em for around 70 clams a few months back.