These are too gorgeous for words. I took them indoors without flash with my old iPhone 5 as I was dashing past a florist on the way to collect Ziggy from the vet. The florist is in the tunnels of the underground so the lighting was not very good.
I did not go in to have a closer look, but I have made roses like this before. Not with such a vibrant effect though.
You carefully split the stems into a number of sections and put each section in a small glass of water mixed with food colouring, taking care not to stretch the stems too far or they will break. The plant draws the colour up to the petals through the stems by means of the water. The more food colouring you add and the longer you leave them, the brighter the colour will be.