Liquid MSU type fertilizer turned grey-blue is it ok?

[Becca]

For the fertilizer guru's....my liquid MSU type fertilizer has turned a grey blue color. I mix it into a liquid concentrate and keep the big batch in a gallon container, and then a smaller proportion of it in a 32 oz opaque bottle and refill it as needed. I keep both containers in two separate places...one in the basement in the storage room where it stays dark and the other under my kitchen sink where it is handy! Both containers probably don't get any cooler the 50 or 60 degrees. Anyways....I've noticed lately that both containers changed colors....from it's vibrant blue color to a dark grey-blue....is it ok to use? Is it still good? I got scared and started to poor it out and then stopped thinking some one on here might be able to tell me if it is still any good before I waste it all down the drain.