Chlorine tests that turn yellow are OTO kits that can only go to 5ppm. The Phenol Red test that accompanies it is the type where you add 5 red drops to a water sample and then do a color comparison (shades of pink/red).

Though not ideal, you can kinda get by with dilution to test your water using distilled water. (Not super accurate though.) Another way to kinda get by is by using an off the scale color matching chart that shows you higher chlorine readings using an OTO kit. Copy and paste the following link into a browser window while you are NOT logged into the forum to be able to see it.

http://pool9.net/oto/

But....... you would still have to know your CYA reading. Does your pool store do the 'disappearing black dot' test to test for CYA? That is the only way you are going to get an accurate reading. Knowing your CYA reading is critical.