Pre-owned pearls do not tend to hold their value on resale, but many folks succeed in selling the ones they no longer want, especially if they are particularly unusual or beautiful. Realize, however, that there are a gazillion freshwater pearls on the resale market. These may be hard to sell...
Bead nucleated freshwaters with very thin nacre (see this bare patch), photographed under studio lighting to bring out the colors. Certainly not good quality.
I couldn't tell much either. Not sure if they are FWP or SSP.
The dark yellow ones, even if SSP, could be color enhanced with dye (dark gold SSP are considerably more valuable than lighter gold or yellow colors.)
Lots of folks like wearing dyed freshwater pearls (I have a strand myself), so yes, they do have value. But nowhere near the value of saltwater pearls of natural color.
If you are interested in learning more about pearls, may I suggest you take the "Pearls As One" course? I will DM you a code...