Note that blue has not always indicated ion weapons in the films. The clone troopers blasters emit a blue blast, but if they were ion weapons they would have less effect against organic targets and wouldn’t be good for killing Jedi later on.

Also, the planetary ion cannon in Empire fires more of a pink blast.

Nerd response: Technically AT-AT’s can be destroyed by aircraft. The problem is the power difference between different vehicle’s weaponry. The Snowspeeders in Empire have blaster cannons, a weaker version of a laser cannon intended for lighter armor and anti personnel. Something like an X-Wing is armed with laser…