From what I've read of Texas law it is legal if it lights up white or amber, but I haven't gotten a good yes or no answer yet.
In the front of the vehicle, it has to be white or amber or any color inbetween.
Taken directly from Texas State Statutes...
(d) A turn signal lamp shall emit:
(1) a white or amber light, or a color between white
and amber, if the lamp is mounted on the front of the vehicle; or
(2) a red or amber light, or a color between red and
amber, if the lamp is mounted on the rear of the vehicle.