Both red and green salsa are essentially the same thing except for the peppers used in the salsa and the taste and color.
Red Salsa uses and is made with ripe Chili peppers while the green Salsa uses the less ripe green chili peppers to make it.
That is what makes the green salsa green is the green peppers and the red salsa is red because of the red chili peppers.
The red salsa is usually hotter than the green salsa because the the red peppers are more ripe and hotter than the less ripe green peppers.
Other than that there's not much difference between red and green salsas.
Green salsa also sometime uses tomatillos instead of red tomatoes.