How does a television show different colors in the scenes?

Answer 1

There are different kinds of TV but the conventional tube-type TV can do that because of something called a Cathode Ray Tube (CRT). The surface of the TV screen is layered with tiny tiles that are different colours, kinda like this:
_______
|_RED__|__
___|__BLUE |
| Yellow|

And the pattern keeps repeating all across the screen. The Tube envelopes the screen from behind and gets smaller as it goes backwards to the back of the TV (like a cone-shape), where there's something called an Electron Gun. The Electron Gun shoots electrons at the backside of the screen in a particular order that stimulates the tiles on the surface of the screen to show their certain colour. By mixing those colours (the three optical-primary ones: red, blue, yellow), you can make any colour. By putting all of them you get white, and by not having any electrons make contact with a certain patch of tiles you get black.

That's why the TV is sometimes called "the tube"

Answer 2

The camera has four picture taking tubes, one for white, one for red, one for blue and one for green. The electronics at the station sends signals from each of these tubes in succession over the air to your receiver. Your TV set sends a signal to tiny dots on the screen in exactly the same order as they were generated by the camera. If you get close to the screen, you can see tiny red, blue and green dots. The white signal provides brightness, luminance, to the picture. These dots are lined up in 525 lines down the screen. The picture is "sprayed" on the odd numbered lines then the even numbered lines. In the US, we get 30 complete pictures a second. In Europe, it's 25. That is based on the fact we have 60 cycle AC and they have 50.

The hard part for some is knowing that red and blue make magenta. Blue and Green make cyan and red and green make yellow....light. Don't mix paint that way, but in light it works.