Ok, here is the final version using resin!
The “resin in pockets” method of coloring is quite nice, although getting the shade of red correct requires trial and error because I was using “cure to white” resin, so the red dye would interact with the whiteness of the resin, but only AFTER it cured. [I couldn’t find white dye, so I had to buy a “cure to white” resin to get the white color…]