Sorry!

There is a learning curve on chlorine tests. There are 3 tests:
1) OTO. This is simple and reliable and comes in the cheap, $5-$10 test kits that test chlorine and pH. But it's got two limitations--the kits usually only measure to 3ppm and a FEW go to 5ppm--we frequently need measures up to 15 to 25ppm. Also it only measures Total Chlorine. The good thing about OTO is the color gets more and more intense with higher chlorine even if you cannot measure it.

2) DPD. This is a test capable of measuring chlorine levels up to about 10ppm--but the test kits rarely go above 5ppm. It can measure both Free Chlorine and Total Chlorine, allowing calculation of Combined Chloramines (which, if more than 0 means something's growing). But above a certain point, the chlorine BLEACHES the tests making them look like you have NO chlorine. For these reasons I don't like DPD.

3) FAS-DPD. This is the gold standard. You don't need to recognize shades of color--you add a powder to get a colored solution and then you add drops until it goes clear again. You can safely measure up to 50ppm of Free Chlorine and it also measures Combined Chloramines. (you get TC by adding Free Chlorine and Combined Chloramines). If you use FAS-DPD testing, you don't need to use any other chlorine tests.

Also there are strips, but to me, they only indicate if you have LOTS of chlorine or need to measure it with OTO, DPD, or FAS-DPD.