What you might want to try is to set the HSB values in the Special Dialog and then write the corresponding CMY/RGB values down to a macro. That might work if you need the same colors each time.
Attribute ColorRGB1 at value; ColorRGB2 at value; ColorRGB3 at value; store preset 4.x

Other option might be to create the presets but store them as universal presets. That way fixtures using the same attributes can use these presets as wel, even when adding them at a later time.

Last but not least: add your colors to the swatchbook.xml file. That way you have your custom colors in the library and than they can be recalled thru macro:
fixture x at Gel "name of your gel library"."name of your color"

Best regards
Mark van der Meulen
Bavel, The Netherlands