You mean in that chapter where she completed her seal? That could've been dirt. But even if it was a blush it's not something to make a big deal out of.
Characters tend to blush when they get excited, whether there's romantic feelings involved or not. Sakura was not happy that her "love interest" came to her, she was just glad for having Sasuke's backup given it hadn't happened since the good old Team 7 days.
I know, it could've been both. While we shouldn't make a deal out of it, it indicates that she still has feelings for him. If it actually was a blush, but I think it was. But it's mianly because of 540 I think she's not completely over him. She's taking one step at a time.