I noticed this on one of my angelfishes the other day and I was initially disturbed as it wasn't what i expected for the female tube. It has a red-pink coloring that appeared to actually break the skin. However, after reading LH's sticky about sexing angels, I was confident that it was normal.
Half the reason, I was surprised is that I've had the angel for over 2 years and this is the first time I've seen the tube displayed.
55g: Planted Tank: Firemouth, Blue Acara, Rainbow Cichlid, 15 Bloodfin Tetras, and 8 Panda Cories
45g Planted Tank: 2 Koi Angelfish, 19 Rummy Nose Tetras, and 6 Green Cories
20g Planted Tank: 8 Harlequin Rasboras, 4 Peppered Cories, and 8 Amano Shrimp