Need assist with a mass color replace

[smooreace]

Im a little stuck... I have approximately 700 files that I need to do a color replacement on. I've done similar prior, but the first time around it was replacing 2 specific colors. The new images are as the sample attached. I can fairly easily do this by selecting all of the blue, tuning the edge selection, and changing tone. But that would take hours to do manually.

So the end goal is to change all of the blue tones to browns. The end result is making a modern-looking map into something appearing as it would have if found on old parchment.. so the blues have to go! 

Is there a batch process, or script, that make this easier than a fully manual click-fest?

TIA