Not really a problem but if you leave argon oil brand hair dye on the bathroom shelf for 8 months it changes color. I used it last summer to get a cool mermaid email effect with their electric teal. Upon uncapping it again today it looked a bit purple. I used it and some punky color turquoise and voila, it is indeed purple. Now I'm rocking space hair. It's important to note that the punky color also sat on the shelf and was used on the mermaid hair. So now I've used the same dyes twice with two totally different outcomes. I'll get pictures up once I get it cut.
It might be more sensitive to light or warmth than the crazy colour. Even with the same brand dyes, some dyes will change colour in certain circumstances and others won't. Like there was some special effects, I think it was a red shade. After a while, some would have a gold cast to them in the bottle. In that case it didn't change the outcome as far as I remember.
That's what I was going to mention Janine, my Special Effects Nuclear Red used to get an almost shimmery gold cast to it after it had been open a while, but yeah I don't recall it being any different once applied.