Shields in Star Wars are visible when interacting with the atmosphere but not outside of an atmosphere. In TPM, Anakin's fighter exhibited a shield effect inside the Trade Fed ship when the droids shot at him, but the same fighters in space (and the Queen's ship) didn't show any shield glowing. These are the same shields but look different depending on where they are. Various ships shown in space do not have shield glow when they get hit, except for some Trade Fed ships in ROTS, which had a sort of blueish shield effect near the beginning. But this battle does take place in the upper levels of Coruscant's atmosphere (DVD commentary).