All I can remember about it is that it’s a mech anime that there are 2 groups that use mechs and some alien/demon things they’re all fighting as well as fighting eachother. They transform into the mechs with a whiteout near nude scene that has ther silhouettes visible and is caused by a crystal they wear somewhere on there body like a necklace or bracelet. One of the 2 groups uses green crystals “Goodish guys” other group uses purple crystals “badish guys”. I also remember 1 purple crystal lady decides to fight with the green crystal ppl. If it helps at all this anime is probably at least 20 years old or somewhere near there I watch it as a kid in the late 90’s maybe early 2000’s.