Responding to this thread as it pertains directly to my product and I've not heard from the poster yet...
*Pure* Nicotine starts as a very pale yellow- almost clear. With time, it will age into a darker and darker yellow, to even a bit orange. Keeping it in the dark, away from oxygen, and cool will slow this process.
Even at 100mg (10%) levels, nic will oxidize a bit, but the presence of other chemicals, like PG or VG, will change how quickly and sometimes even the color. In my personal experience, it generally slows it down from what I observe in pure nic.
I could name several other vendors who sell nic that turns pink (or yellow, or tan...), and even a couple who ship it that way. I'm sure they would agree, a much better indicator of the quality is the smell and taste, rather than the color.
In my opinion, both as a vendor and as a vaper, I'd say that liquid is just fine and would have no qualms using it. If you try it and decide it's not up to snuff, then talk to me and I'll try to help you.
I'm always reachable via email:
rob@bluemistvaping.com