It's fun that your aura is lavender.
It sounds like it suits you.
Your aura color and third eye color should change according to your own "energies" (where you are on your lifepath, what is going on in your life, your mindset, emotions, etc).
It's really easy for me to tap into my third eye. I do it at least weekly, sometimes more. The color varies depending on what is going on in my life but it is usually blue (lighter blue, not indigo) and orange. I also see green or purple. Once in a while, it is red.
You don't have to pay someone to see your aura. Just meditate or sit in padmasana in front of a mirror. When you open your eyes (after a few minutes) you will see your aura in the reflection. Last time I did this mine was a combo of pink and green. I haven't done this for years, though.
From my point of view, the color should teach you about self and the info isn't important to the outside world, especially because the color can fluctuate.
I can also see other people's auras sometimes when they're just sitting with me. (This isn't something I can do on demand.)
Any color can fit an INFJ depending on what they are experiencing in life at the time.
