Was it regular granulated sugar or was it a coarser or finer grind
Back in the 70s when our first local coffee boutique/roaster opened, House of Coffee Beans, I was very in to gourmet coffees and accessories. One thing I bought there several times was 'coffee sprinkles' (not sure if that was the product name). This was a small bag, about 5oz. of variously colored small sugar crystals, slightly larger than regular granulated. The idea was to add it to hot coffee in place of regular sugar but not stir. The crystals settled to the bottom of the cup and slowly dissolved, so as you drank your coffee, it got progressively sweeter, and the bottom of the cup was like coffee flavored candy.
I don't use sugar in my coffee or tea normally but I kind of liked this. However, one drawback was the top of the coffee became oily from the various colors (dyes?) and was a little unsettling to look at. I haven't had any in years; I decided I didn't need the extra sugar in my diet.
Anyway, the point of all this
is they obviously had to dye these various colors separately.
I went googling for 'coffee sprinkles' and came up with a company in WA that makes flavored coffee sprinkles, but that's not what I used to get.