I have tried using both 1156 and 1157 LED bulbs when I had clear taillights and both showed a nice deep red... at night. In the day, you can't see a damn thing. Plus with the turn signal LED's they automatically turn into "hyperblink" signals.

Your best bet would be to either paint the bulbs with the same paint people paint their taillights with (Transparent Candy Apple Red), paint the taillights red, or go back to stock.