It should be green or brownish. I cant tell color in the pic with your lighting. Could also be cyano on top of it making it look more purple. said:
Some of it is brown, other areas of the tank have more of a dark lavender tint.
On a side note, I am finding the testing of phosphates to be incredibly annoying. It seems to me that if you have enough for it to cause problems like cyano and hair algae, the nuisances created by it are using it all up so you read zero on the test. I am thinking that I don't really care what the actual number the test returns is... I just need to decide which of the following categories my tank falls in:
A) Tests Zero or near it and no sign of nuisance algae- Everything is good. Have a beer or three to celebrate.
B) Test is greater than .03 but no sign of nuisance algae- Levels are creeping up. Put down the beer and deal with it now before it causes a problem.
C) Tests Zero and nuisance algae is present- It isn't really zero, but you should know that just by looking at the tank, so I don't know why you even bothered to test. Throw in the towel and grab a bottle, or hunker down for the long term and start dealing with the problem. Don't even bother pulling out that test again until all the cyano and GHA is completely gone, because you already know the test isn't going to tell you anything.