dark blue nipple when pumping

Megan • Happily married💒, Mom to 7(4👧 & 3👦)

Hi ladies! im exclusively pumping and the last couple day i think, i have noticed that my nipple turn a dark color when pumping. like very dark purple/blue. Has this happened to any one else? is it just bruising or what could it be? it goes away after in done. it just freaks me out i dont want my nipple to like die and fall off lol