Never made Red Velvet before, can I use the BC red gel tubes?
If you mean the decorating gel found in the grocery store cake decorating section, I don't think it will be red enough for that RV look. Having said that, if that's all you have, and you are out of time, I'd go for it! (Unless the cake is for a customer, of course). Then let us know how it works out!
I think those are red colored piping gels? not sure if that will work as good! If you have time to run down to walmart, buy the wilton brand gel color in the little container, I use the no-taste red and it works great! just dissolve in about 6 tablespoons hot water or your cake will be unevenly colored!