Colorware is now offering its mail-in custom coloring services for the iPhone 3G. Available with either solid or metallic paint for a total of 35 color options, each selection comes with a high-gloss, scratch resistant finish formulated to protect against minor scuffs from normal usage. Coloring for the back only costs $150, while the frame ($20), home button ($20), SIM card tray ($10), and earbuds ($10) can all be colored as well, for an extra charge.…