red,yellow,blue r fundamental colors, but in electronics these r red , yellow ,green. why?

Answer 1

Paint colors which absorb light are different than the electronic monitor colors which transmit light.

You mix red, yellow, and blue pigments to get all the paint colors.

You mix red, green, and blue phosphors on a color monitor or TV to get all the light colors.

Answer 2

it depends if you are adding light or subtracting light.

in colouring, painting, and photography you are looking at reflected light coming to your eyes. The white light shines on your object then you see the reflection, here white light (all colours) gets absorbed (subtracted) and the result is left to reflect into your eyes, so to mix other colours that are subtracting (reflecting) you need R B Y.
If you are looking at multiple sources that generates light, they are adding to each other and what your eyes see are the result of addition (like a TV screen, multicoloured LEDs, or pixels of a computer screen, all these are mostly electronic devices). So the primary colour you need, in addition, to make the range of other colours are R B G.
Note that there is a relationship between the 2. Since
YELLOW = GREEN - BLUE

Answer 3

There are two ways of defining colors; what we see and how the frequencies work. The first has to do with pigments while the second is based on physics.

If you take the three pigment primaries and mix them, you get the secondaries. If you take the three other and mix them, you get secondaries.

With pigments, you are seeing the color that is not absorbed by the substance. With the frequencies you are seeing true color.