Okay kiddo, have you ever looked at a picture and noticed that everything in it looks a little bit yellow or blue or some other color? That's what we call a color cast.
Think of it like wearing colored sunglasses that make everything you see that color. If you wear yellow sunglasses, everything will look yellow, and if you wear blue sunglasses, everything will look blue. That's kind of what a color cast does to a picture.
Now, why does this happen? Well, sometimes the light that we use to take pictures isn't perfect. It might be too yellow or too blue or too something else. When that happens, it makes the colors in the picture look a little off.
But don't worry! If you ever take a picture that has a color cast you don't like, you can fix it. It's kind of like taking off those colored sunglasses - you just need to use a special tool called an "adjustment" in a program like Photoshop or Lightroom. Then, you can change the colors in the picture to make them look more like what they would look like if you were looking at the scene with your own eyes.
And that's color cast in a nutshell, kiddo!