Freshwater Pearl Colours

These are some freshwater pearls I bought recently - aren't the colours lovely? I have some ideas of how to use them, but it made me wonder - how do they get to be such different colours? So I did some internet research!

http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/pearls.html
says that
"Freshwater pearls are noted for their wide range of color, they can be found in white, silvery white, pink, salmon, red, copper, bronze, brown, lavender, purple, green, blue, cream, and yellow... The different colors are a function of the mussel species, genetics, water quality, and the position of the pearl in the shell. Generally, pearls assume the color of the shell in which they form."

http://www.pearl-guide.com/pearl-colors.shtml
says that
"Pearls come in a wide variety of colors, ranging from white all the way to black. Here again (as with many of the characteristics of pearls), the fact that the pearl is an organic gemstone, formed within a living creature, contributes to the myriad unique ways in which its coloration can develop. The bodycolor is determined by the type of oyster or mollusk that produces the pearl (certain types of oysters generally produce pearls of certain colors), as well as the conditions of the water, and sometimes the type of nucleus which is implanted to stimulate the pearl's creation."

So, a combination of natural and man-made factors is implied here, which leads to another question - what different nuclei are used to make pearls?

http://www.madehow.com/Volume-3/Cultured-Pearl.html
says that

"The materials for cultured pearls sound simple; they consist of an oyster or other mollusk, the shell nucleus that is to be implanted, a tiny bit of live tissue (from the mantle or lip) from another oyster, and water. Producers claim freshwater pearls are more natural because nuclei are not used; instead only a piece of mantle is implanted to culture these pearls. All the materials are natural, although human intervention is required.'

Other sites also agree that it is a bit of 'mantle' used, so that is that question answered. But back to the issue of colour.

http://www.pearl-guide.com/pearl-colors.shtml also says that
"It is important to note that many pearls are artificially colored. This is widely practiced with freshwater, akoya, and at times Tahitian pearls. The colors are artificially infused by a treatment known as dyeing, or by subjecting the pearls to irradiation. These treated colors are typically easy to spot by a trained observer who may peer down the drill hole looking for concentrations of color, which indicates the presence of dye, or a darkened pearl nucleus, which indicates radiation treatment."

But how do non-trained observers tell? The drill holes of my pearls are far too small for me to be able to see down, and would I know what to look for? Does it matter, when creating jewellery, to be able to say? In my use of pearls I have always described them with their size, approximate colour (grey, or grey-purple, for example) and that they are freshwater - is that enough information for buyers? I'd be interested to know what you think!