Short answer: Yes, email
info@ultrasaber.comLong answer: Funny I also original ordered a Sentinel LE V5 in Fire Orange but I will warn it is on backorder at the moment and might be 10+ weeks, worth checking when you email them.
Additionally I added a lot to my order with additions to my lightsaber and additional extras so changing the blade colour should be easy and fine. Because of the likely wait time for your chosen hilt it will be even easier to be honest as it shouldn't be built for a while.