Weird test result for Alkalinity

[sabres07]

I was testing a friends' pool today for alkalinity with the Taylor 2006c kit. I put the 5 drops in and the solution turned green, as it should. But as I added the next drops in, the green did not turn red, instead it turned blue and eventually to yellow! I am fairly new at pool testing, but in my own pool, this test always went good......turning from green to red. What gives????

A little background here: this pool is currently at shock level (Chlorine 25 ppm, CYA>100) because he is battling an algae bloom. Does a high Chlorine count affect the ALK test?

[waterbear]

High chlorine levels will bleach out one of the dyes used in the TA indicator solution so instead of turning from green to red it will turn from blue to yellow. The test result is still valid but the endpoint is a bit harder to see. You can add an extra drop or two of the thiosulfate (the first reagent) to counter this but it is not necessary if you can detect the blue to yellow color change without problems. Ideally this test should not be done when the FC level is high.

[sabres07]

Thanks so much!