Thanks for starting this thread so interesting!

It is also about the photographer...the quality of the light in the room when the picture was taken...the camera, etc. It's a gamble. I wanted some dark eggplant fabric, and the picture online was really like dark blue, but the person said, No, it's purple. I trusted that it was the right fabric and bought it, and luckily it was right. But, if I hadn't known about the fabric ahead of time, I wouldn't have believed the dark blue was really dark purple.