Don't think it's been mentioned in the forums here yet but the Sister of Temptation has 2 skins: a blue only (the color shown in the pet's profile image) and a color-changing skin which can show up as red or blue, both in the pet journal and on summon. It's unrelated to the breed - I have 2 H/Bs right now and one is stable blue while the other color changes. Don't know if it'll get fixed (though if it does, I really hope they'll just turn the color changers into red), but for those who have to have one of each skin, it's something to look out for.

EDIT: After reading comments below and doing some testing, it appears the color changing skin is either unstable or temporary, or that something got fixed in the reset this morning.