The Yellow bumble bee, Bombus fervidus is the primary species in this group. Tergites (upper abdomen) segments T1 thru T5 are yellow.
Another species to mention is van Dyle Bumble, B. vandykei. It traditionally falls in the “no red, yes stripes” group, but when I encounter it in the field I am often struck with how much yellow it shows.
Yellow head bumble females, B. flavifrons often show striking bright yellow on T1 and T2.
The yellow form of the California bumble bee, Bombus californicus also shows a lot of yellow.
The Nevada bumble bee has golden yellow on its thorax and T1, T2 and T3.
Other yellow bumbles that are commonly seen on the westside are drones/males of the Yellow head bumble bee B. flavifrons and the Fuzzy-horned bumble bee, B. mixtus.
Notice the rear (3rd) leg (above). Notice it is hairy and relatively round–no corbiculum. Big clue it is a male.
Males often have extra hairs on their upper lip (sound familiar?) giving them the appearance of have a mustache.