I would not recommend using these drugs in an insulin pen. The insulin pen injects insulin intramuscularly. Intramuscular (IM) injection of street drugs is not very safe, and IM or IV GHB sounds extremely unsafe and unpleasant for a number of reasons. In addition, I'm wondering what type of insulin pen you have, disposable or the type that you put new cartridges in? It is not good to reuse the disposable type, as it wouldn't be sterile and the needle would have dulled from using it before. If you have the cartridge type I guess you could put a new needle on it but I'm not sure how you would fill the cartridge or reservoir, the whole thing just sounds like a bad idea and a hassle. IM injection of ketamine is done, but I would not advise you do this with anything less than a micron filter and a fresh sterile syringe. Maybe try some safer ROAs, especially if you are new to these drugs.
We also can't tell what's in your GHB just from the color, I believe that falls under drug identification, which is not allowed.