I used Wild cherry flavored Jello this year and you do get a nice red color. Previously I've always used food dye but thought I would try it. Haven't fished with it yet so we'll see. As to whether it works or not...we'll see. I use a brining method so just add the jello to the brine and dissolve. Color wise, in the past I used to always use Procure, double red hot or something like that for my curing. Seemed to get catch fish fine. On the other hand, I've used orange colored roe as well and it too works. When fishing natural baits, I suspect the stronger incentive is scent first and then sight which is why even if you're fishing with yarn adding a scent attractant makes sense. As Grumman said already, the darker colored roe is easier for the fish to see in colored water and certainly having 2 or more different colored roe is just more arsenal in your bag of tricks. A lot of it still has to do with confidence. You will always fish better with a color YOU believe works rather than one YOU don't believe works as well.