So far, we've learned that Photoshop doesn't see color. Everything in Photoshop's world is made up of black, white, or some shade of gray. We've also learned that Photoshop uses the RGB color mode to display colors on the screen by mixing different combinations of red, green and blue. But how does Photoshop know how much red, green and blue to mix together for each color on the screen when it doesn't see colors to begin with? I mean, it's great that Photoshop can display pure yellow by mixing red at a full strength value of 255 with green also at 255, but how does it know to display yellow in the first place?

The answer is, it doesn't.

Huh? It doesn't?

Nope, it doesn't. Photoshop doesn't know that you're expecting to see yellow in a certain part of the image. All it knows is that it's supposed to display red at 255 and green at 255, and to leave blue out of it. If that makes a certain color that you and I call "yellow", great, but really, Photoshop couldn't care less. All it knows is "display red at 255, green at 255, and blue at 0 in that specific pixel". Whatever color that ends up being to you and I matters not to Photoshop. When adding colors to images, Photoshop is strictly a "paint by numbers" artist.

Alright then, so all Photoshop knows is to add a certain amount of red, green and blue. But how does it know how much of each color to add when all it understands is a world of black, white and gray? Two words... Color Channels.

Let's look at our bird photo once again:

That's how you and I see the image.This is how Photoshop sees it:

But wait, there's more. This is also how Photoshop sees it:

But how can it be seeing it in two different black and white versions? Good question. The answer is, it doesn't. It sees it in three different black and white versions. Here's the third one:

What we see as one full color image, Photoshop sees as three separate black and white images. Each one of those images represents a color channel. The first one was the red channel, the second one was the green channel, and the third was the blue channel. Three separate channels for three separate colors, all coming together to create the full color image.