I've had peprika mixed in the powders I use while dusting, so they aren't the main ingredient, as well as had it in the FF medium, it kinda works.
The best solution I had to that issue was actually what I fed my tricolors, at the time I had my groups I was actually using very few FFs and almost completely pinheads I was raising up from the 2000+ crickets I was ordering a month for my gecko colonies. This was actually cheaper (since I had to order the adults anyways) and easier at the time for me because I was handling so many crickets. Gutloading the crickets was as simple as having a sweet potato and romaine lettuce diet and you could actually see the guts of the pinheads due to the orange of the sweet potatoes. This not only colored up my tricolors, but was actually how NAIB raised their pinheads (what they mainly feed) and the color change in some of their red pumilio was noticable as well.
Beware of beta carotine suppliments, its very strong and could be toxic to your animals if not used correctly. I think Brock is actually the one with a tank of BJ pumilio that he sparingly uses BC on to keep their color but I don't remember the schedule of supplimentation. I believe it was as little as once a month.
The slimming down of the stripes in F1s is actually a myth if not just miscommunication. Some bloodlines of the same morphs will have less broad stripes that others. Broad striped animals of certain populations are only variations in pattern, sometimes occuring in something like 10% of the population. This 10% occurence happens in at least one 'santa isabel' population, where the back is almost completely yellow, instead of having just the yellow stripes. I've also had a morph of 'anythonyi/salvias' where one of my adult breeders was a broad stripe (the rest were pinstripes) and I only had one froglet out of around 100 that had that pattern show up on, and not even out of that broad stripe female!
Are you breeding your frogs and seeing this occurance?