Im not too sure about the forever part but it is normal for them to change colour quickly. Mine did. Then again my whole body did. I started gaining water weight at 4 weeks. And showed a basketball by 12 weeks. Now im 30 weeks and dont even remember what my old body looked like.
20 weeks & my nipples look like 2 big black oreos without the cream & I'm fairly lightskinned toned.. they've been like that since I first found out I was pregnant at 7 weeks, you'll be fine trust me. Out of all things that is gonna change about your body your nipples is onlt minor.. lol.
they got bigger and all that even before i confirmed my pregnancy. but now they are just so dark! my nipples have never been like that! I'm kinda lighter skin so i was so shocked when i looked at them! i just can't believe its all changing so fast! lol i just thought i had more time you know...