Gabriel only matches color-wise, but it's pretty much a tunic over strange plated armor that covers his entire body.
Simon wore tights with normal plate armor. And it was amazing because he wore tights.
But yeah, the outfit itself is just as distinct from the classic heroes as any of Ayami's, in terms of actual clothing details, ornamentation, etc. It's its own thing, which I'm sure they were intending considering it was the base for the other Brotherhood members. It's pretty unique.
Stubbles are just added hair though. I guess it's a design element used to make Gabriel seem brooding or despaired, which is pretty off from traditional Castlevania Belmonts, but his outfit just communicates something a lot more differently to me than his stubble, because stubbles used in design nowadays are also usually used to make heroes look tougher, so it's all in-line with the old barbarian design. Same end goal, different approach.
i really have no idea what his outfit is supposed to signify besides the belts and utilities. i guess it's the same as WARRIOR like the skimpy barbarian outfits considering his inhuman proportions and ARMOR, but it just feels diluted to me by the tunic. idk im just traikgifngfgd;ghgfhgfh