I can't take credit for the color-changing bits; that feature was there in the original Bootstrap template.
If you're asking about "3 columns" meaning "sidebar plus middle content plus sidebar", take a look at the Configuration :: Layout Settings :: Response {Left | Center | Right} Column Width settings. The sum of those values should add up to 12, with the default being 3 + 6 + 3.
If you mean "how do I show my products as a grid of 3 columns instead of 1 per row", which is built-in to Zen Cart v1.5.7, look at Configuration:: Product Listing :: Columns Per Row
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