The polythene films used in manufacturing bipyramidal tsetse traps in the Central African Republic can exhibit slight variations in colours. Experiments using a new protocol that combines a Latin square design and two competing traps in the same experiment conducted on Glossina fuscipes fuscipes show that a iess intensely blue colouring decreases the attractiveness of the trap. Polythene is useful material for tsetse traps, but is necessary to verify that its colouring is homogeneous.