Yes Jalapeno peppers do get hotter when they turn red as they ripen further.
Green Jalapeno peppers are already pretty hot when you pick them off the pepper plant.
But if you want hotter Jalapeno Peppers you can let them stay on the Jalapeno pepper plant and then when they turn red the peppers will be hotter.
As Jalapeno peppers get older and ripen further they increase in heat which is why some people will hang them out and dry them outside in the sun.
My neighbor years ago used to hang Jalapeno Peppers out on her porch and they got hotter as they dried out in the sun.