I had to learn how to take my spool valve off my tractor because I could not afford to have someone else do it. I has to figure out a method of hydraulic hose identification if I was going to be successful.
My quick and easy method of hydraulic hose identification is simple. Use colored zip ties to mark the controls for each individual spool valve and then use the same color ties to mark the lines coming out of the valve. Since each valve has a input and a output I used two zipties on the lower hose and a single tie on the upper hose.
Even if I get the input and outputs confused the smae fluid goes to the right cylinder and what happens is the control works opposite.
Meaning if I got the lines reversed, but still stayed on the right valve (color of ties) pulling the lever to raise the boom would lower the boom.
This is not a problem, but confusing the lines and mixing different cylinders could cause problems.
This simple method saved me hours in taking my valve off and putting it back on. I had to do this what seemed like a hundred times as I ventured back and forth to the hydraulic shop to find out what was wrong.