I went through a stage of having fluoro yellow, fluoro green, fluoro pink, orange, white, purple, or yellow as the fish in the lake I was fishing at the time would change what they wanted or would accept week to week or session to session.
In one winter for a couple of weeks, the working pop-up was Green Zing, fluoro green, then it was Pineapple in fluoro yellow, a couple of weeks of popped up sweetcorn, then Monster Crab in orange on one rod, and Squid and Octopus in pink on the other, and orange Tutti Frutti produced the occasional fish.
The Strawberry ice cream in red failed to catch, The Secret in purple caught a few, then all of a sudden halfway through a week session in winter, coloured pop-ups stopped working and from then on every fish came to Smokey Mackeral food source bottom baits.
When I moved onto Nazeing I simplified my baits; Squid and Octopus (pink) and Monster Crab (orange) were close to the Smokey Mackeral in terms of smell, so I used them as the top bait on a snowman, and caught regularly on that, along with a dark red Garlic Oil and Spice combination of my own, used as pop-up topper or as pop-up.
Bromeswell in spring last year, the pop-ups that worked were The Secret, and Pineapple Juice.
On the reservoir last season I just carried my Garlic Spice combination, and fished that on one rod. If I caught on my food source bottom bait, (KMG) I didn't catch on the pop-up, and if I caught on the pop-up I didn't catch on the bottom bait. A few fish this year have come on snowman baits, a pink KMG pop-up over a KMG bottom bait.
You can either get every flavour or colour combination going, and keep chopping and changing, until you find what works, although fluoro yellow Pineapple are a pretty good cert on many waters, possibly confusing the heck out of yourself, or just get a couple of pop-ups, maybe one to match your bottom bait and that pineapple, and have faith.