Color - the nemesis of all designers. Have you ever noticed how you might view a certain object as green, while someone else insists it's blue? There's actually a very good reason for this.
Perception is everything. The human eye is too complex to explain in a blog post, but an important element is the cones within the retina. These cones are responsible for sending signals to the brain, telling us what colors we're seeing. The interesting thing is, everyone's cones are different. That means everyone's brains are receiving slightly (or very) different signals about what they're actually seeing. While this is super cool science, it's also a designer's nightmare.
"We want a green logo." Great. Okay. What does "green" really mean? Take a look at this page: https://www.pantone.com/color-finder?q=%2356B15D And that's not even all shades of green! This is why there are "Pantone" colors. These are standardized colors which eliminate the guesswork. While we may disagree about how a certain shade of green looks, Pantone 2256 C is still Pantone 2256 C no matter where it's viewed. In the printing world, colors are mathematically produced by varying degrees of cyan, magenta, yellow and black (CMYK). When selecting a Pantone color, the CMYK formula is revealed so it can be reproduced correctly.
Generally speaking, whoever is in charge of a project (say, a logo) will choose the color based on what they see onscreen or printed. It's our job to find a color that both satisfies them, and that can easily be reproduced by printing companies (whether it's a poster, a t-shirt or paint for the wall). Bear in mind that colors we see onscreen are produced by light, while colors we see on printed items are produced with pigments. But that's a whole other topic in itself.
Color may be a scarier world than most people think, but it's also a very fun world full of infinite possibilities. And we love the sound of "infinite possibilities."