When dyeing clothing, it is often more practical to purchase a set of primary colour dyes along with black and white than to buy a specific colour dye for each project. In the case of hot pink, it may be difficult to find the suitable colour in the store; it's also a colour which cannot be easily substituted. Hot pink is quite different from any of the other pink dyes you are likely to see in the store.
Add red dye to a plastic container. Decide how much red to use, according to how much cloth you are dyeing. The mixture will be around two-thirds to three-quarters red, depending on the shade of red you are using and how light you want the hot pink to be.
Slowly add white to the mixture at a ratio of around one part white for five parts red. mix the dyes together with a stirring stick.
Add blue to the mixture, beginning at a ratio of 1 part blue for 20 parts mixture. Slowly add more blue if needed. Stir the mixture with the stirring stick. The blue will give the pink a hint of purple that makes it a hot pink.
Test the dye on a spare white rag. Let the rag dry and decide if the dye needs to be darker, lighter or needs more blue. Add one or more of the dyes to alter the hue as desired.