Purple (Deep Blue? Blurple?) and gold works! This design is pretty rad and would stand out in a good way.
Some review items:
Be wary of your soft parts being dark vest on dark flight suit, monotone makes it harder to read the layers. If the fabrics are different weights and/or weaves they will catch light and weathering differently and fade at different rates, so it may not be a big issue. Just keep an eye out and make sure they read as distinct layers. Making one layer lighter will eliminate the problem and keep the overall monochrome feel, but it is not required by any means.
Yes, kamas are permitted in P/I CRLs (under Soft Parts -> Other Soft Parts -> first item in the list: Kamas are acceptable and can be of a canon or custom design. Kamas must cover at least 1/3 of the total waist circumference.). Since they are one of the options for an accessory that's required for Gunslinger, I'd plan on having one, since dusters aren't permitted in P/I and a poncho would cover up your sweet paint job.
Loincloths are not permitted for P/I(Last item covered, in the same list as kamas). Your concept image appears to have a cod also; skip the loin cloth and you'll be fine.
Since you are thinking brigades, and your armor level is looking Medium to Heavy, you'll eventually need the cod plate anyway. For initial app you
could skip it, as you have six of four lower body armor pieces. You might also consider applying with shin plates and knees, and adding thighs and cod as part of your Gunslinger upgrades.
For your shoulder armor, you can scale and trim away at the profile of Din style pauldrons, or you can use Fett-style, or you can create a custom variant that's unique to you. As long as they are mounted well and sit comfortably they shouldn't interfere with your gunslinging. Keep your Ruus'alor in the loop and check through the
Q&A if you're doing custom designs.
Similar to my thoughts on the leg and lower body armor, you might have the bicep plates be part of upgrades for Application Round Two: This Time It's Brigades.
Keep in mind for Gunslinger: in addition to the minimum of three pistols and a scattering of knives (1 combat knife or 3 throwers, or a combination 1+2), you'll also need a short-barreled two-handed blaster, and at least one explosive. There's other required accessories but that's a problem for Future Sessik.
Minor things aside, this is a solid looking design and I'm looking forward to seeing it getting built.