Believe it or not, it’s kind of both!
The color pigment in plants that makes red is called anthocyanin. The pigment normally reflects red light waves. But if you raise the pH and add a couple metal atoms to anthocyanin, it changes the light waves reflected – and poof – blue!
Turns out, blue is a pretty rare color in nature. Dr. David Lee wrote a whole book about how colors in nature come to be, including the fairly complex steps to making blue in “Nature’s Palette: The Science of Plant Color”.
If you’d like to check out the color pigments in the flowers around your home, visit Scientific American for an easy, do-it-yourself pigment experiment.