While I was coloring in my Barda pin-up, I realized she looked just fine with just flat colors (last drawing above). Kirby's use of solid blacks and pattern are so well controlled they act like a form of 'shading' that makes his characters so strong even with just simple flat colors applied to them. So the scales in her uniform act as a gray and her gloves stand out because they're the brightest 'shade' even though they're really just the same color.
Personally, I kinda liked the flat colors that were used on Kirby's characters back inna day more than today's gradients/'modern' colors. I guess I kinda understand why now! I think a lot of his DC work has the flat color process more in mind than his Marvel ones. Or possibly his later designs just leaned more towards that style (like his eternals designs)? Or maybe I'm just reading into it too much?