I missed the line you wrote that the pic was of your pool, of your old color. I thought you were showing a pic of the color you wanted. Do you not like that color? It's awesome!
What I actually did about my color choice, contrary to what I was suggesting about the images, was just match my previous plaster. I already new I liked it, and how it would look in my pool, in my yard. The plasterer first came out to my pool, and I told her I loved the color of my pool, but wouldn't mind if it was a bit darker. She determined I had Tahoe Blue plaster. We discussed a bit that possibility that my pool had evolved over time, lighter or darker, and my concern was if I just said "Yes" to Tahoe Blue, would new Tahoe Blue pebble match the color my pool old Tahoe Blue plaster.
So then I went to the showroom, to feel what pebble felt like on my feet, and started fooling around with swatches. And she even brought out plastic boxes with pebble, with various additives (dry, no plaster). She'd throw in a little of this color pebble, a little of that. I got frustrated, because how was I supposed to know if a swatch I saw on the wall inside, or one I laid in 6" of water on a step in their demo pool, or a box of beads, would translate to the color I wanted when it was applied to my pool, at depth, in my yard, surrounded by all the stuff that affects pool color!!??!! I don't think that's possible!!
She sensed my frustration, and I sensed hers. She finally gathered up all the samples and declared "I know what you want." And that was it. She determined the color, she claimed she darkened Tahoe Blue a bit, and she was dead on. My pool color is exactly what I wanted.
Which inspired me to share with others not to try and pick the color of your pool from a swatch, but rather find something to hand or show to the plasterer, and make them match it. That should be their job, not yours. Which, of course, depends on the cooperation and skill of your plasterer. I just happened to have one that was willing to do it that way, and did it well.
So here's an alternative: If you want the same color, or a slightly different color, you might try an onsite visit with your contractor (the guy that's actually going to mix the color). Discuss the color directly with him/her. You could say: this color, but slightly lighter (or darker). Or the shade is good, but a little bluer (or whatever). Or if you want something completely different, then bust out the images. Then let them translate your description into the color name. A color that will look the way you want, in your yard. That's what worked for me. If I had picked the swatch, I doubt I would have gotten the result I wanted, and conceivably it could have been wildly off...