Nicole Brunelle did a post on Facebook that got a zillion replies and lots of discussion. She has a pet peeve that sellers are using photoshopped pictures. While most responses were supportive that this is a problem, many posts explained why photos are adjusted or in most cases why cell phone pictures often appear to be photoshopped(because the phone does the adjustments).
Yesterday, I showed Margaret my picture of Hollyhill Tarantula that I have shared with many people. She exclaimed: "that is is not good picture, it is a lot more purple than that. " It was the original picture that was just cropped. I opened up Photoshop and adjusted the purple color a bit and she said: "That is not enough, but it will have to do."
There is no answer for this issue.
One method that I tried a year ago to address the issue was to select a companion flower that has a nice blend of colors and picture the subject flower with it. If the companion flower is a well known flower, people would be more likely to trust the accuracy of the depiction of your new flower. 
I have better example of this idea(that are somewhere and I may look for them) but does this picture quality?