I think the dye is useful so you can see through the fuel line when priming the carb and also, you can see it in the tank so you know when you are running low.  I like Blue Thunder as it seems to run cooler than Sidewinder, but I can't get it easily.  I use Sidewinder Race, and it seems fine.  Backyard Basher I avoid at all costs.  Engiens run way too hot and are touchy to tune.  As above, I suspect the high oil content causes this.