Yeah, with cheats, when you do a permanent alteration it tells you that it will be permanent. I would assume the same is the case if you get high enough light level that it tells you what will happen when you don't have cheats enabled.
Basically, if it doesn't explicitly say that your change will be permanent - assuming you have cheats on, or have the sufficient light for it to tell you what will happen when you use the light - then it's temporary, at least in regards to any mental alterations, or transformations (bimboification, gender swap, youngification, etc).
That being said, every light has lasting effects on whoever you use it on. So if you you use a temporary mental light (like temporarily making Nadir your mommy), that will affect her, but only slightly, and unless you lean into similar style of lights on a particular person, any one minor light shouldn't prevent you from accomplishing something with them later, even if it is contrary to what that minor light was (following that previous example, if you had previously made Nadir your mommy temporarily, but later wanted to, say, enslave her with a green light contract and no mental alteration, there would be no issue, and she would not act as your mommy at all going forward).
In most cases it requires an accumulation of actions - especially without cheats - to affect a character enough before they are actually changed, without the use of a major light.
Green lights seem to be the only ones that have "permanent" effects across the board, though, as the characters do not forget their actions while under their effects.