This is how I get the true color of a lipstick without the pigmentation of my lips affecting the color.
1) Moisturize your lips. I used Blistix chapstick.
2) Apply your regular foundation all over your lips. Make sure to get the corners and edges of your lips. I used Maybelline Non Stop All Day Wear Foundation.
3) Line your lips with a lip liner that is similar to the lipstick you will be using. I only lined the center of my lips.
4) If you don’t like the regular harsh liner of lip liner, smudge out the line with your finger.
5) Apply the lipstick of your choice. I used Revlon’s Softsilver Red.
Let me know if you try this, and how you think it works. :)