I am quite happy with my pH meter, I am not good with colours. I frequently verify the calibration with a buffer solution, but I don't often have to recalibrate, reading remains stable for weeks.
What is more critical in my case is to be very thorough about contamination. E.g. after verifying the calibration with a buffer solution, I first rinse with distilled water, shake it off and dry with a tissue. Then I rinse and shake off multiple times with the pool water to be tested before doing the actual test. And then I make sure to wait long enough for the reading to stabilise.
My tester also works much better when stored in storage solution. But that influences more the time it takes to stabilise the reading, rather than the accuracy.
If you don't store in storage solution, then you should add at a drop of tap water to the container around the electrode to keep it hydrated. Never store in distilled water, that basically pulls ions out of the test head, that can destroy it. If it just dries out, it needs to get reactivated with storage solution (in my case 3 molar KCl).
