To be fair, dogs know more about flowers than this. We often assume other animals share our emphasis on sight, but images can only scratch the surface of a dog's scent-centric existence.
Still, we know dogs lack the ocular equipment to see red, and a 2017 behavioral study backs that up. Using a modified version of the Ishihara color vision test, researchers found that dogs perform similarly to humans who are red-green colorblind. Dog vision is blurrier, though, since they have four to eight times less visual acuity. That's roughly 20/75 vision, meaning dogs lose sight of patterns from 20 feet away that most humans could see from 75 feet.