what do you think will happen on earth if the sun turns green?

Since green light has a higher energy than yellow light that would mean that the sun would suddenly have started producing more energy for no apparent reason. As far as we know, this couldn't happen.

However, the light from the sun could also turn green if the light was undergoing a doppler shift due to the movement of the sun in relation to the Earth. For the wavelength to be increased to green, the sun would have to start moving towards the Earth at a very high speed.

I think you can guess what would happen to the Earth if the sun suddenly came flying at us at a very high velocity.

The Earth will say, "Hey! Sun! What the hell is wrong dude?". Then it will run over to the Sun, realise that the Sun is choking on a chicken bone, and give the Sun the Heimlich maneuver and save the Sun's life.

The Sun will be forever grateful and shine on for another 5 billion years.

Then the Sun will get Alzheimers and forget that the Earth saved it's life. The Sun will get senile and turn into a Red Giant and destroy all life on Earth.

The end.

The sun can't turn green. Stellar colors are blue, blue-white, white, yellowish white, yellow, orange, and red. Colors reflect the temperature of the star. The sun, a G2, while officially yellow, is to all relevant purposes White. Green is not a natural option. If you see a green sun either your vision has gone bad, an advanced alien civilization is playing tricks, or the fundamental properties of the universe have changed. Occam's razor suggests the former.

The sun is green- it's peak power output occurs at about 550 nanometers.... well within the green band of the visible spectrum. This also just happens to be the color to which our eyes are the most sensitive and the wavelength to which chloroplasts in plants are the most reactive. Riddle me that, Batman ;-)

That would be very bad for most plant life on Earth, since green plants *reflect* green light, so they wouldn't absorb any of it.

That means all the other spectra of light won't reach us anymore, and we will all die a gruesome death.