If you’ve just done it, then an Undo operation would reverse things on all the images, I think. But if it took you a while to see the problem, then you might have done something to cancel the undoability.
Isn’t Blue Filter a built in LR preset that modifies the HSL settings: http://kb2.adobe.com/community/publishing/924/cpsid_92473.html
Open the HSL panel and step back into History on one of the affected images so the effect of the Blue Filter preset has been undone and notice what HSL sliders change, and then if the 650 images DON’T already have any HSL adjustments you should be able to sync JUST the pre-Blue-Filter HSL adjustments (perhaps all zeros) to the other 650 images.
Thanks for the reply. Unfortunately I dicovered it after a couple of changes, so I can't undo.
I found the "blue filter" in the Lightroom B&W Filter Presets. It changes 6 sliders in the Black & White Mix panel. By the time I go through each image individually to see if there were changes made to the Black & White Mixer, it is just quicker to advance through each image while in the develop module and set the history back one step. Long and tedious, but quicker I think than loooking at the Black & White Mixer and then stepping bgack.
Any other thoughts.
If you can’t tell which photos have the issue, then maybe you’ll have to look at them one-by-one. I thought you knew which ones.
Can you make a preset that consists of the settings you need to undo the B/W Mixer adjustments and apply that to a group of images, even if some of those don’t have B/W Mixer adjustments?