Are you meaning the color of the shrimp? health issue?
Fish naturally enjoy little foods in the habitat. Invertebrates are foods for many fish. Any item which can fit into the mouth of a fish can become food.
So, it is possible that a couple/few male Guppies or Endlers might cohabitate fine with adult shrimp. It gets trickier when there are babies, and most people want babies. They are small, tender and delicious little snacks for fish.
Sometimes an aquarist will allow the shrimp population to grow to (or buy) however many adult shrimp you want to observe in your tank, and then purchase some fish to live together, aware that the baby shrimp may continue to populate the tank or some eaten and some get to adult size.
It depends on your objective. Many people want to breed shrimp and sell some to make some spare hobby cash / trade. And many like watching a tank with fun creatures all over.
What do you think your biggest interest is right now?
One other option is to remove the biggest, best, most colorful Cherry shrimp to a breeding tank and enjoy watching the fun antics of the other Cherry shrimp amongst the Guppies.
In most cases of keeping shrimp AND fish together (for me), after fish were removed from the tank, the population of shrimp increased in a big way!
Also females of the Guppy and Endlers are voracious monsters and look high and low for foods (to further their growing babies), so I absolutely think having females would be a huge detriment to the colony of shrimp.
