How do Blue potatoes differ from Yukon Gold potatoes?
There definitely is a difference in flavor, although it is rather subtle. I find that the blue potatoes are a touch richer or more "potato-y" than Yukon Golds. However, in cooking with them I've had plenty of success doing direct substitutions. Other than the blue color being a little odd-looking in some recipes I think you'd be safe just swapping one for the other in most cases.