Its okay to be a "newb" we all start somewhere. Steampunk doesn't have to be earth tones to be accurate. The main reason you see mostly earthy tones is due to the era steampunk is based off of- during the 1800's, most people couldn't afford the dyes to make their clothing more elaborate, so everyone wore Browns & beiges...
That being said, since you're wanting an aristocratic feel to your outfit, go for jewel tones. Deep blues, emerald green, ruby red, etc. I'd go for brocades, damasks or jewel toned statins for vest fabric. As far as finding the right vest pattern, look under historical patterns. Some companies have steampunk patterns now, but historical patterns should help you find something close to what you want.
And a side note on the aristocratic aesthetic, there are a few accessories that denote wealth in steampunk- glasses instead of goggles. Goggles are more of a working class piece, while glasses with colored lenses or a monocle denote wealth. A pocket watch chain dangling from a nice vest pocket also helps sell the aristocrat look. And maybe a top hat with a more delicate decoration, like peacock feathers, gives the look of money & helps sell the overall aristocrat vibe.
Hopefully I have been of some help. Feel free to message me if you need anything else.
-2016 cons & costumes-
SC Comi-Con (Saturday)
ArtDeco Rogue- X-Men (completed)
Human Raava- Legend of Korra (%60)