Doesn't seem like a very blue ability.

Blue in this set doesn't really mean blue. It means Japanese. None of the colours in this set particularly correspond to their canon counterparts.

I try to match the flavor with the color pie, sometimes this works quite good, sometimes (like here) it may feel a bit odd. I started by thinking witch color represents witch party best, from the beginning it was clear that black is Germany (what else than the color of evilness could represent the nazis) and red is the soviets (would feel very strange to build a Red Army in an other color). That left me with 3 colors to go, very soon I decided that white should become the USA, it fits flavorwise as well as mechanically (lots of creatures and many flyers). So what about green & blue? Well first i wanted blue for GB and green for Italy but then the Axis would be on enemy colors (not good!) so there was only blue left for the second axis party (all against black is something I don't want to do) and that felt much more like Japan than Italy. When I started here, green still was intended to represent the UK, but as green is rather grounded I thought France would be better fitting and still work flavorwise. TL;DR: If anyone has an idea for a mechanic that feels blue as well as japanese: you'r welcome!

I'll just note that enemy colours can be temporarily "allied" in certain settings. The most notable recent example is Mirrodin Besieged, where green and black were mostly Phyrexian, red and white were mostly Mirran, and blue was split down the middle. So I don't think it'd be a problem to have the Axis on colours that traditional Magic calls enemies.

I also don't think it's necessarily clear cut that the Nazis have to be black... fascism, for example, is generally a concept within white's colour pie, and white can most definitely be evil (e.g. Konda, Lord of Eiganjo). The Nazis' ethnic cleansing, fuelled by paranoia, could also be white or black. I don't think anyone'd argue that black doesn't fit - it's obviously fine as well - but I don't think it's a completely automatic choice.

The Soviets are tricky: communism is extremely white and somewhat green, but you're right they do have a strong mental association with red. In the same way that a goblin scientist is red not blue, or an elf dictator is green not white or black, I guess it's fine to have the Soviets red.