Can I calibrate 2 screens to match, without buying expensive gear?

I use a 2010 Cinema Display and a 2011 Thunderbolt Display, both connected to my 11-inch MacBook Air. The screens are ever so slightly different in terms of how things are reproduced.

How can I get both screens to render things the same?

I know I could buy expensive color calibration hardware, but its really not worth it to me for a one-time use. Instead, is there any other way I can do this? I have a pretty good eye for colours (which I guess is why it bothers me in the first place?) and so perhaps there is some kind of tool that lets me do this by eyeballing it?

Solution 1:

Personally, I'd go with the expensive option - you have a grand's-worth of screens there; why not have them both accurately profiled?
The first downside of manual calibration is not knowing which of the two is 'more correct' in the first place - the second is actually getting them both to look the same...

Back in the good old bad old CRT days I always used to set screens up by eye - since I bought a colorimeter, I haven't looked back.

If you do decide to go for a colorimeter, avoid the entry-level Huey Pro, as it no longer works on Mac. Bottom of the line these days is probably the Color Munki Smile, which is quite adequate for 'in-house' calibration, if you don't need a fully-calibrated workflow to printers/publishers etc.
You can also do PCs & your iPhone with it, if you want ;-)

Anyway - if you want to try it manually, the functionality is built right into the OS itself...
System Prefs > Displays > Color > Calibrate... [you get one on each screen, though it doesn't look like you can run both at once]

Clicking that launches the Display Calibration Assistant,

which you can run through as many times as you like; save with a different name each time & review later to see which you're happiest with.

I didn't quite dare to actually run the assistant at first - didn't want to mess up my own calibration ;-) When I did try it I discovered there seem to be far fewer tweakable options than there used to be - you used to be able to adjust per 'gun' colour balance, amongst other things. All I got to pick was a white-point, which really isn't going to be of much use :/