I have to say I have not found it to be the way. Our first Pug was the very pale and creamy but he got darker because he got the dark guard hairs in his back and both the other two were and are very similar. If we are talking newborn, them yes they do, all fawn puppies are quite dark and they lighten to what will be their normal background colour with the guard hairs appearing later. I hope that helps.
What color is yours and how old? When fawns are born, they are often born very dark in color. Then lighten up over the next few months. Same with apricots...you will often see a lot of black hairs in an apricot puppy, that will dissapear over the next few months. Even our rare silvers lighten up a whole lot by the time they reach 8 months old. Our silvers are born silver, darken a bit by 5 weeks old usually, then lighten up a whole bunch by 6-8 months old. By a year old we see the color it will keep. Not all pug puppies do this. We have one mom who gives birth to very light fawns, and do the opposite by darkening over the next few months. lol Over all, yes pug puppy colors do lighten, or darken. If the breeder knows her dog, and what kind of puppies she produces, then chances are she knows what she is talking about when she says the color will lighten. But just to be curious...how old is it, and do you have any pictures? ..there are always those who will say anything to keep you happy. :P
"And now we have lost sweet Tin Tin, beloved by Puggirl. Pugs come into our lives to brighten them, and that is exactly what they do. Sweet Tin Tin, please find our puggies that have gone on before us and tell them we still remember…"