I was trying to figure out what the rationale was behind making the the lieutenants gray.

We've gotten them mixed up with heros a few times during games and moved the wrong pieces. It seems a bit confusing that they are the same color as the heroes. Wouldn't it have made more sense to make them red like master monsters, or possibly some alternate color like orange?

Or green.

I would've preferred purple, as all villains wear purple.

That said, I actually like that they made them gray. It makes them seem on par with the heroes, and they essentially are the Overlord's own heroes.

You could try painting them red?

For people that paint their miniatures I imagine.

ArmyPainter make coloured spray primers. If you really dont want to paint your minis but you are really annoyed that they are grey and would like them a different colour altogether it is not difficult at all to spray them another colour instead.

Edit: In fact if you want painted minis, but want to put as absolutely little effort in as possible the army painter system could be for you . You basically prime the mini, paint all the different areas on the mini one solid colour each, then dunk them in quickshade, then shake and let them dry. No blending, layering, dry brushing, blah blah blah. Its not how i am painting my own minis but from what i have read on the net they will look playable with this method, the biggest advantage is that it does not take much time to paint them like this.

NO! Right Color!

Like Ringskipper menitoned, they are the Overlords equivalent of a hero. Like a Dark Link! Grey brings that concept visually. I love that they did that.

white would have been a good choice, neutral but a bit different from heroes.

Well I can see why they would want to avoid red and tan as colours for LTs. If they were red, people might start thinking LTs were master monsters. Likewise, if they were tan, people might get confused and think they were minions.

LTs are monsters, but they are neither master nor minion.

"Hero Grey" is the only other colour of plastic they're using in Descent.

Making them some fourth colour would probably have incurred extra costs, which would in turn have bumped up the price tag, and I think FFG was doing everything they could to keep the costs down. I know I, for one, was surprised by how cheap these LTs figs are priced. Plastic minis are generally only cheap when sold in bulk.