Rohrer and Klingner Blau Permanent comes from Germany and is a medium-light blue whose name is perhaps a little misleading....my initial impression was that Blau Permanent meant I would find a 'permanent' or 'waterproof' blue, but this isn't really the case. The ink's permanence leaves a bit to be desired. It's better than most of the other R&K inks (with the exception of the iron galls), but aren't as good as some of the other permanent blues out there like Noodler's Midway Blue and Bad Belted Kingfisher.
What this ink does have going for it is a fast dry time, just over 10 seconds on Rhodia, which is pretty ink resistant paper. It would be even faster on most other papers. The colors is very pleasing, a pure blue that has a moderate amount of shading. The flow is not too wet, not too dry, right there in the middle somewhere. Like all of the other R&K inks, this one cleans very easily out of pens. I didn't see much of a difference writing with a medium vs. EF nib, but the broad did darken up the color a bit. Because the pen isn't heavily saturated, you're going to see some variation in the darkness of color based on the pen you use.
There are several inks that are in this color range:
Blau Permanent comes in a 50ml bottle, and is available at GouletPens.com in both bottle and sample form. I do sell this ink, so read my whole review with that in mind and use your own research and judgment to determine which inks are best for you.
Check out the other Rohrer and Klingner reviews I've done:
If you've used Blau Permanent, I'd love to hear what you think in the comments below!