I'm on a laptop, so it looked white or pink or lavender, depending on how I
tipped the screen.

I don't know about the technical end of this computer business, but not only
does the light you use to shoot the shell make a difference, so does the
camera itself, be it the type of film or the adjustment of the tube or
whatever techy thing is on the film plane these days. Then you've got the
color balance on whatever screen the viewing audience is using.

Not to mention that the background the shell is shot on can effect the
viewers perception of that color. I remember a really snappy display at the
Astronaut Trail show last year that feature a collection of shells with
purple pigment all displayed on a drapery of lush purple fabric. It was very
impressive, but I remember thinking that the purple in the shells would have
really popped out on a yellow background, yellow being the compliment of
purple.

Then there's the stuff that can't be adjusted, like the viewer's personal
optical equipment. For example, I see colors slightly warmer out of my right
eye and cooler out of my left eye. It is very subtle and I would have never
noticed it except that years ago I had to do numerous rather tedious
exercises for a color theory class.

Color reproduction is tricky, tricky, tricky. And as far as stability in
printed material? Whew! Even the shells themselves have trouble with that.