First things first, yes, check the box. They're spelled "Froot Loops," not "Fruit Loops." We know, right?
Second, the outrage. Honestly, is there no end to the high fructose corn syrup lies? It turns out the "fruit flavored" circles touted by Toucan S[c]am are actually just "froot-blend"-flavored.Yep, all those pretty ROYGBV dyes don't mean diddly, since each color tastes exactly the same!
Q&A site The Straight Dope (via Reddit) reports that, just as that blue tropical bird mascot hasn't changed since the cereal's creation in 1962, neither has Froot Loops' flavor — that's flavor, singular. According to Wikipedia, "The cereal pieces are ring-shaped (hence 'loops') and come in a variety of bright colors and a blend of fruit flavors (hence 'froot')," and not "fruit."
Of course, not keen on destroying precious childhood memories, we decided to do a little blind taste testing ourselves, only to find that each loop does in fact taste like mildly sweetened cardboard, with negligible or no differences between them.
(Method: We handed our three blind tasters random samples of Froot Loops and asked them to guess which color they had been given. The results were pretty sporadic, with nearly each color being wrongly identified as around three or four others. The yellow loop, for example, was guessed to be red, orange, and purple twice; the purple loop, red twice, and then yellow, and green. Our Trix and Fruity Pebbles tests afterward yielded similar results.)