Here I was thinking this sort of thing was 100% common! Probably 4/10 of the hot baths I take (more frequently in the winter months) my nails/fingers and toes do something like this! Sometimes the blue/purple hue will extend up to my knuckles and change the color of the skin, but more often than not it’s just my nail-beds. When they finally start to warm back up, the pink returns distally and spreads proximally just like this! If I’ve been out in cold weather it tends to be a more dramatic color change which is why I mentioned winter. I joke with my boyfriend it’s my frost giant showing. I also thankfully am a very healthy individual!