Monitor Color Calibration?

I have a set of ViewSonic TFT monitors at work. They are arranged in a square grid with two 24" at the bottom and two 27" above.
I'm admittedly not that great at figuring out how to adjust my screen color settings.
I can't get the ones on the bottom to do whites very well, nor do they match the monitors up top. The top monitors could be a bit better as well.

I know there's spendy color calibration tools out there, and I always assumed that's for photographer types, but I look at these things ALL DAY for work, so why not have something to get them dialed in better, right?

Does anyone have a recommendation, either just a 'by hand' method or a tool? Please note that my work doesn't allow me to install ANYTHING that hasn't been passed through the network security team, so go with the idea that I'd either have to bring in a personal laptop to do the job if there's software to use.

 

I've used this tool in the past. It's open source so you may need to work through some issues but generally it is solid. I believe it works on all platforms, as you didn't mention what os you are on.

https://displaycal.net/