If you're talking about the theme from http://themes.shopify.com/themes/minimal/ you'd need to replace the 'social-icons-light-bg.png' image contained in the theme (similar to the below) with a colour version.
and where would I get the html?
Not quite sure what you're asking here. You would edit or create a new image in an image editing application such as Photoshop, Gimp, Pixelmator or even Illustrator (in this case). HTML editing isn't required as you're replacing the PNG file.
Where did you find the color file?
This isn't the first post that I've seen people asking for this so I quickly put one together. It will sit on my CDN until I decide to remove it. It's not perfect, but will help if you're totally stuck. It also exists as a vector file should someone need it...
Go forth, you colored dots of destiny.