with nitro there are only two places in the us that make nitro as far as i know either cal. or tx.they are getting ready to open another methanol plant here in south east VA they make methanol in a lot of places.the only difference in fuel would be the type oil and and of course nitro content.the color of the fuel is just the manufacturer adding dyes.the best thing to do is go by what the engine maker suggest.i do however add some extra castor to my fuel due to the older engines i use and some added protection. i run 10% nitro fuel in my engines.some people here swear by 15%.but for the type flying i do and the variety of engines i use and the extra cost of 15% i will stick with my 10%