I put something up in the suggestion site at uservoice as well, but I thought I'd list it here.

It's the second time that I've been hit by this -- a competitor is playing a gray color, so when I touch one of their countries and they show up I think that it's a blockade.

I ignore it and then get clobbered the next round.

Another fix would be to have a unique color for blockades.

Players can not use the same color (gray) as the neutral armies (including wastelands).
So, maybe you are color blind, or your monitor had some color calibration issues, or you looked at it in a wrong angle.

some of the colors are similar to the grey color, especially if you aren't watching too closely...

I've had people not notice me before when they clearly should have because of my color of choice