In which I overanalyze the Super Turtles' eyes
For one thing, we never see their pupils. The Ninja Turtles similarly have all white eyes behind their masks but we see black pupils when they take them off. I've always thought the Ninja Turtles look oddly naked/exposed without their masks but it's an infrequent thing, usually reserved for when they're off their guard or off the field like when they're just waking up in the morning.
We never see Grav or Shelle take their masks off so it's no surprise their eyes are all white when they're wearing them, just like the ninjas', but Blob and Grid don't wear masks and their bare eyes are still all white, even within the safety of their home base.
I've seen the white eyes attributed to the turtles' nictitating membrane/third eyelid, a real life thing which serves as a defense mechanism to protect their eyes (In some continuities like 2012 we see it kick in when they go on the offense, aggressive/on guard. That's a real life thing too, sharks may activate this membrane when attacking prey) Annnd naturally that cues me to read too deep into it and see an insinuation that the Supers don't feel like they can drop their guard or be exposed in those small ways even when they're off the field. Defense mechanisms are default for them.
And another interesting little tidbit I noticed thanks to a post I saw way back (sadly I don't remember who made it, hopefully I find it again sooner or later / EDIT: this post!) noting the difference in shape between Leo and Raph's eyes vs. Don and Mikey's eyes. The sharper/more serious-coded brothers' eyes being more angular, the gentler/kinder-coded brothers' eyes being round and looking a little more innocent/youthful.
In the Supers' case, it's Shelle, their Don, whose eyes are sharp and Grid, their Raph, with the rounder, softer eyes. That little design choice does fit the comments a couple people have made that Shelle comes across slightly more brusque and "all business" than our Donnie but seeing their tough guy Grid with those big sad eyes and knowing what he's been through just gets to me, man
