In both cases the antenna is just a bit of wire "tuned" to the transmitted frequency, in this case 2.4Ghz.
RC and AC both have two, linked antennas, in the RC the two little projections from the rear and on the drone they run down the front legs.
A full wavelength at 2.4GHZ is 12.5 cm. and this seems to be the length of the "bits of wire" for drones. (I think my calculations are right ?)
Different colours, no idea, colour will make no difference to performance, it's the copper wire inside that does the work. Mine are all grey.