I took a couple of photos of a hand dyed yarn tube that I was unraveling and winding onto a paper core in preparation for knitting a pair of socks on my NZAK circular sock machine. I figured I'd try one with a light source above it, and one without.....choosing to post the one which showed the truer color. Trouble is, they both do.....it all depends on what light the yarn is in, so I'm posting both for your comparison, too.
With the light, the colors show their warmer side........so it's pretty clear the light bulb, a regular incandescent, brings out the warmer tones in the dyes.
While using just natural indirect light, their cooler aspects come through.
I guess this just goes to show that you can't really tell what colors truly look like unless you see them in person......and then it will depend on the lighting, but at least it will be seen through your eyes and not someone's lens. ;)