Would a black or white colored inground pool be easier to heat?

Would a black or white colored inground pool be easier to heat?

A black bottom pool will be slightly easier to heat than a white bottom pool, but the difference will be very, very small.
Yes, some very small amount of extra energy will be absorbed by the black color and absorbed into the water that would otherwise be reflected by the white color pool, but this small amount of heat is dwarfed by the large amounts of heat that are lost or absorbed by the water due to air temperature, wind speed, evaporation, cover, heating method, etc.
Most people choose their pool color based on design and/or looks and then get a good pool solar cover to help keep it warm (regardless of the color).