As has been repeatedly explained here, use of a VC emulsion will cause problems when used in a colorful environment, as it will give variable contrast depending on color. Adding red sensitization will mess things up further.

A fixed grade emulsion OTOH is easily pan sensitized by adding either a pan sensitizing dye or a green and red sensitizer. There is another thread here that describes this type of work. But, many claim to have achieved pan sensitivity, but I have seen little evidence to prove it. Doing it in color will be proof, but doing it in B&W is not proof.

Ok, now for the dyes, you add about 50 - 100 mg of dye per mole of silver while the emulsion is melted. Hold it for about 15 minutes with stirring and the deed is done. The temp should be about 40C. These dyes can be purchased from Sands Corporation in Florida. The dyes dissolve in either water, ethanol, or similar solvents. They give that information. Expect to pay several hundred dollars per gram. These dyes are expensive.

OTOH, Holmburgers has posted a list of less expensive dyes. These might be useful.

In Germany, Honeywell sold dyes.

AND: NEVER FREEZE A LIQUID EMULSION!

PE