a compatible protease and phophatase inhibitors mix - (Dec/03/2007 )

Dear All
when I added phosphatase inhibitors (sodium fluoride and sodium orthovanadate) to cell lysis buffer containing protease inhibitor cocktail (supplied with clontech apoalert cell fractionation kit), the solution, basically colorless, become colored (light yellowish). dose this reflects some sort of interaction that affect the efficacy of the inhibitors? if so, is there any recommendation about a compatible protease and phophatase inhibitor mix?
thanks

I see the same colouring when I prepare my protein cell lysis buffer for western blot, I think, this is only due to the sodium orthovanadate. If it is not very fresh everytime, or even, if it is fresh, it gives normally colourless solutions a sligth yellowish colour. But I don't think this will interfere with the function.