To answer the initial question, I'd say no. I've done plenty of research on liquid cooling before as I was interested in picking up a some-off 750 dollars liquid cooling setup, but in all I read, everyone was pretty well dead on with "do not mix fluids" as well as "don't use colouring liquids" and all teh things of the sort.
To flush the system out, just pull the line that hooks back into the reservoir and run distilled water through the system. Be sure to put a bucket or something under the line that you pulled. do this for 5 to 10 minutes and let it air dry the tubes out. When it's all good, (I'd suggest 10 hours to FULLY dry) hook the lines back up and put your new liquid in. I suggest Feser One as I've heard good reviews. As some have said, tend to stay away from UV reactive liquids, they not only can get murky, but can affect the performance AND even erode your lines.
I can't exactly say how you should keep your components cool while you run your PC...
Grantofhell :d