With the new information on Kyber Crystals, we discovered that the only colors Jedi will end up with for their lightsabers are blue, green, or in rare cases purple.
Yellow Lightsabers, like the ones used by a starwars.wikia.com/wiki/Jedi_Temple_Guard, are assumingely specialized or synthesized specifically for the Temple Guards. These Lightsabers are designed to be a starwars.wikia.com/wiki/Lightsaber_pike (double bladed lightsabers).
However, in starwars.wikia.com/wiki/Dark_Disciple, we find that starwars.wikia.com/wiki/Asajj_Ventress acquired a yellow Lightsaber off of the black market... starwars.wikia.com/wiki/Ventress's_lightsaber. This lightsaber seemed to be a normal lightsaber that a normal Jedi would use, not anything similar to a Temple guard lightsaber.
I highly doubt that a Temple Guard lightsaber or anything related to it would end up on the black market. This lightsaber must have belonged to an active Jedi, probably similar to a starwars.wikia.com/wiki/Jedi_Sentinel.
So, if this lightsaber is not related to the temple guard lightsaber, does that mean it was built using a yellow Kyber crystal? Or a different type of crystal?
*** moved to the 'HOF:Discussion' category. ~CLG ***