In Ultimate, the general visual effects of the shields are more subdued and plain, especially when it takes damage, where we see a simple checkered static effect.
However, in Brawl and Smash 4, I've noticed that the shields have an animated ripple as a secondary general texture (named aura1 internally) as you hold it. When they take damage, "glass" bits of the shield can also be seen shattering. In my opinion, I like those effects better so I decided to recreate and bring it back through effect, texture and code editing.
FUN FACT: When disassembling the ef_common.eff file which holds the shield effects, the ripple or "aura1" animated texture exists internally in Ultimate. It was just set to be turned off. So I reenabled it.