any way to have multiple projects open to adjust exposure/color across them all?

I am editing 3 different videos in 3 projects, that were taken on my iphone. because of iphone's automatic WB and exposure they all look slightly different. What's the best way i would go about adjusting all 3 to look the same without switching projects and just trying to "remember how they looked". is there a way to have all three open in final cut pro so i can adjust and match all 3 by eye? is there a better way to do this?

You can only have one project viewable at a time, but you can use the Comparison Viewer in FCPX to save frames from any project within your library. This way you can select a frame from another project and have it viewable alongside your current timeline clip to match coloring. See this Ripple Training tutorial on how to use the Comparison Viewer:

Drop them into a Timeline, any old project timeline, temporarily. Create a grade that works, or two grades, or three. Save Effect. Then you can just drop that preset on to those clips. Use names that let you know what grades go with what clips.

If you don't want to create one-time effects presets, put all clips from one camera into a Compound. All clips from another into their own Compound. Then grade the compounds together in a temporary timeline. Then edit using ranges from the Browser, they'll all match all the time.