I am no Betta expert myself, and continue to learn everyday from my fish and from the forums. My understanding is that if he turns pale, that could be a sign that he is stressed or scared. Mine is iridescent blue/green, and when he is stressed or scared, he turns pale and becomes a different colored fish all together with a dark stripe running along his body.
Generally, turning color is a way for them to disguise themselves and blend into the surrounding if threatened or scared.
I may have overlooked if you had mentioned it, but constant temperature is very important, and so a thermometer is what you need to monitor the water temp since you will be doing water changes on a daily basis, otherwise he will be shocked by the varying temp.
Hope he will be upgraded to a 2 gal soon and feels better!