Theoretical entitlements:
Weld 180, 2 seats
Boulder 291, 3 seats (notice I'm using 2000 figures, before Broomfield County was created)
Adams 363, 4 seats
Jefferson 527, 5 seats
The Census Bureau estimates include a restatement of the April 2000 census figures to the current boundaries.
This gives:
Adams 348
Boulder 269
Broomfield 39
Jefferson 525
Weld 180
This makes your proposed pairing of Adams and Denver more reasonable (or you could keep them separate and give Adams 3 very large districts). Boulder and Broomfield would be paired for 3 districts. No adjustment to Weld or Jefferson is needed.
I have redone the outstate areas to take better account of things like mountain ranges and economic links. Also, you left out Alamosa.
COLORADO NORTH WEST
Moffat, Routt, Jackson, Rio Blanco, Garfield, Pitkin 99K
(note that only all-year route out of Aspen is down the Roaring Fork Valley to Glenwood Springs. A large share of Aspen ski workers live in Garfield County because Aspen is too expensive)
CENTRAL ROCKIES
Gilpin, Clear Creek, Summit, Eagle, Park, Grand 106K
(Added Grand, dropped Lake)
GRAND JUNCTION
Mesa 117K
COLORADO SOUTH WEST
Gunnison, Chaffee, Delta, Montrose, Ouray, San Miguel, Hinsdale, Montezuma, Dolores 112K
(not real happy about including Montezuma, but otherwise next district would be over).
SAN JUANS & SAN LUIS VALLEY
San Juan, La Plata, Archuleta, Mineral, Rio Grande, Conejos, Costilla, Alamosa, Saguache 101K
UPPER ARKANSAS
Teller, Fremont, Chaffee, Custer, Lake 94K
PUEBLO
Pueblo CCD of Pueblo County. 107K
LOWER ARKANSAS & SANGRE DE CRISTO
Remainder of Pueblo County; Huerfano, Las Animas, Otero, Baca, Bent, Kiowa, Prowers. 110K
LOWER PLATTE & HIGH PLAINS
Logan, Segwick, Phillips, Yuma, Washington, Kit Carson, Cheyenne, Lincoln, Elbert, Morgan. 113K.
If Broomfield is paired with Boulder County, then the former Adams County part of Broomfield would probably bring the Broomfield, Lafayette, & Louisville seat up to size without taking out areas nearer to Boulder. This would then give you a Boulder (city) and mountains seat, and a Longmont seat, including Niwot if needed.
6 if separate from Adams. Neighborhoods are too small. Maybe two west of the Platte (NW and SW), then C, NE, S (or E depending on C) and SE.
If you were pairing Denver and Adams, I would look at pairing Aurora with Denver. Aurora is isolated from the rest of the populated area north of Denver. In any case, I suspect Aurora is the largest city in the Brighton & Commerce City district.
Probably Littleton-Englewood, Centennial, and the 3 Aurora seats (South, Souther, and Southest).
Wheat Ridge goes somewhere. It probably makes most sense to have one western (foothills) seat, and stack the other four, north to south. This would mean dividing Lakewood North and South. But maybe this ends up with too much north of Lakewood, and not enough south?
The first would be Highlands Ranch. The town of Sedalia would fit better with Castle Rock.