Hi Hallie, welcome to the salt rainbow...
literally! LOL There are many black and pink salts (some red salts, like the Hawaiian, are labeled red or pink but that's not an industry standard... just marketing). For instance the Hawaiian red/pink salt is sea salt mixed with red clay, the Himalayan pink salt is a land salt (fossilized marine salt) and natural minerals give it the pale pink color, the Hawaiian black salt is sea salt mixed with charcoal, while other black salts may be sea - or - land-harvested (usually with ingredients added to give it a black color) - and some are smoked (fine as either an ingredient or condiment salt) to add flavor and obtain their color. You need to read the packages, and do a little more research besides (if the package isn't helpful), to know what you're getting. In general, these are *condiment* salts (added after cooking), rather than ingredient salts mostly due to the high prices (with the exception of the smoked salts which add something distinctive as an ingredient). Rather than pay $19/lb for a Hawaiian black salt (sea salt with charcoal), I'd rather use my plain old salt, and just char my food (kidding) but it's fun to put out a selection of colored salts on occasional for entertaining.
Hope that helps answer your question(s)!
R.