Welcome to the forum and I hope you enjoy your time on here!
I have bought shrimp off ebay in the past and they do usually add a couple as they expect a few to die from the transport ordeal.
Sexing them is quite difficult until they are sexually mature, so it will depend upon how old they are? Hopefully the female with eggs is carrying fertilised eggs as that will boost your colony soon. The second picture with the lovely colour is probably a female (I think the second shell looks round). There is a bit too much reflection on the glass to even give the first picture any reliable 'guess', but it could be a male if it is of adult size, I can't see a 'saddle' or the circular shell on the side either, but that may be due to the reflection!
Try watching this video as it may help you decide, IF the shrimp are old enough, as younger shrimp look the same so you cannot tell. Cherry (neocaridina) shrimp reach maturity at around 3-4 months so you shouldn't have to wait very long if they are too young to tell at the moment?
Hopefully the egg laden female will have shrimplets soon, the eggs start very yellow (yolk, with a black dot if you can see it will be the eye) and should turn grey as the yolk is used up and that is usually how you can tell whether the shrimplets will hatch soon?