OK, USAAC & its successor the USAAF were
ARMY troops, not a separate aviation service, as many wished. That didn't happen until 1947 with Truman's creation of the USAF, who initial wore Army uniforms with distinctive buttons & insignia. So khaki jodhpurs, brown boots, dark brown horsehide flight jacket is spot on.
The transition to blue uniforms didn't finish until well after Korea.
Consider please the appropriate USAAC pre-1939 shoulder patch for the brown leather A-2 jacket:

This "pinwheel" insignia represented a whirling 3 blade propeller was worn on the left shoulder only.
Hi tech lookin' n'cool huh? Also not readily identifiable, yet perfectly correct.
Captain's bars on the shoulder loops outboard of the jetpack's straps.
A (former) squadron insignia on his chest would be common. I'd suggest the 103rd Pursuit, the pilots from the Escadrille Lafayette who transferred to the US Air Service in 1917.

Or The 94th "Hat in the Ring" Sqdn:

Interwar flying jackets tend to be plainer, & more uniform, than the gaudier WWII varieties we are used to seeing. After all, in such a small service everybody knew everyone else.
Since you want to use the later winged star insignia, how about a helmet 'decal' foreshadowing both the future USAAF shoulder patch, & the issue, quite common USAF early jet pilot helmet decoration:

Yellow & blue were USAAC aircraft wing & fuselage colours.
I think I'd find them, or indeed any sort of official or tribal markings
'busy' & out of place on such an experimental device.
Can't go wrong with OD, or shiny steel,on the jetpack, with tan webbing or brown leather straps, same as his pistol belt & holster.
If you
must, then go with tail markings, vertical blue, horizontal red & white stripes.

A variety of squadron/group specific ones are readily identifiable.

Please pause & peruse a point: as test pilot & pioneer of personal pulse propulsion perhaps plain is preferable, for pulp purposes perforce.
All due respect to Marine Aviators, arguably the finest fliers on our planet, the Corps always got the fuzzy end of the lolipop, hand me down equipment the Navy & Army no longer want or need. Cutting edge gear has never been a blessing the USMC enjoyed. Rocket tech for the Old Breed? Nah..., not happenin'...
Paratroopers go down, rocket troopers, by definition, go both ways...
I trust this further muddying of your creative concepts actually helps...
Valerik
"The French do see arrogance as a virtue."
Dr. Donald Mallard, NCIS
EDIT my miserble spelling & punctuation