I caught this small cat on Lake Palestine - has an odd greenish blue color near the gill plate/head.

I originally called this a blue cat but I was told its a channel.

Tiny Blues are often a shiny iridescent color like that.

You were right in calling it a Blue. Threadfin and smaller Gizzard Shad have that same type of sheen to them in the water. Almost gives off a Chartreuse type glare. That's why pearl/white with chartreuse is such an effective color for predatory fish, I've been told, by people smarter than me.

It is a blue. The channels are more gray and mostly have a few spots.

It is a blue. The best way to determine for sure is to count the anal rays on the bottom fin. A blue has 30 or more anal rays while a channel catfish has 29 or less.

Another way to tell is a channel cat that size would normally be covered with spots... They go away as the age but judging from the size, that is a juvenile and were it a channel it would be spotted...

Interesting