The above image is the original straight out of camera.
The image directly above has been processed in Photoshop with a few tweaks. Including: color toning, lighting adjustments, removing brassy highlights, eliminating white corners and slight transforming.
The color tones are completely subjective and should be done to your liking. There is no right or wrong, only personal preference. I prefer deeper richer reds so that is why I prefer the middle image. Some may find it too flat for their liking. My goal was to create a red velvet look, the bottom image shows some additional tweaks including detail extractor and tonal contrast applied at reduced opacities. I do like it as well.
A tip for when you are photographing red flowers in the sun. Use a diffuser, reflector or both to help control the light. Keep a close eye on your RGB histogram to make sure you are not completely blowing the red channel.