When you're growing Jalapenos in your garden the Jalapeno peppers when fully ripe should be a bright green color.
Then if you leave the Jalapeno Peppers on the plant longer they will continue to get even riper and hotter and turn red.
After the green color the Jalapeno peppers will then begin to darken to a deeper green, then to black, and then to red.
You can pick the Jalapeno peppers when they're green as they are ripe when they're that color or you can leave the Jalapeno peppers on longer until they turn red and get hotter.