How do I recognize an Alien Commander In UFO Extraterrestrials

I've captured several aliens in UFO: Extraterrestrials (gold edition). However, every new alien I capture is immediately executed because he/she/it is not a commander.

How do I recognize which aliens are commanders on the battlefield so that I know which one to capture?

Normally when spotting an alien a red icon shows up in the bottom right of the screen. Double clicking this icon will take you to the alien in question.

When encountering a commander the same icon will show up, however this time it will have a yellow border. This is the easiest way to spot alien commanders on the battlefield. A second sign you're dealing with an Alien commander is the different color of the aliens skin, for example in the screenshot below the Vipon commander has a green skin while regular Vipons have brown skin.