I needed a new Alt/PS belt, and decided to get a new SC belt while I was at it. The alt belt is a Gates green stripe, but they didn't have a green striper for the SC, just a normal Gates belt. Will it makes a difference with slip? How can I tell if it is slipping?

If it slips, it will probably squeal. Even if it doesn't squeal, the pulley it is slipping on will get hot fast, and may show some rubber dust around it. If you suspect slippage but hear nothing, shut if off and feel the pulleys to see if one is abnormally warm. The belt may also glaze quickly from the heat generated from slippage. Gatorbacks have cut teeth that seem to bend more easily around smaller pulleys - don't know the difference in the two Gates belts you describe.

As well you can see the slippage in your boost gauge. It would fluctuate and not react normally.