The most important thing is keeping a consistent light source and rendering style, i saw you got a rough rendering thing going on so did my best to keep that with my paint over
i highly recommend looking at references for armor for how you want to design the armor, and especially for getting a feel for how light interacts with it and try to emulate that-
the best way to make light pop is through having very clear contrast between values, so a very dark core shadow, very bright highlights & light to really emphasize the contrast and depth
for colors it's pretty tricky and a lot to go into, but the fastest way would be to use a layer with multiply for adding darker shadows of the same color, and add glow for adding lighter values, reflections highlights and such.
if you really want to get a great understanding though i recommend getting some color theory books like Color and Light by James Gurney
or Artists' Master Series: Color & Light
you can also checkout ALLA PRIMA II by Richard Schmid, but it might be harder to get a hold of.