A orange-yellow flame means that your not getting enough oxygen to your flame... for every cubic foot of gas you need 24 cubic feet of air to burn
My propane ventless lights fine, but if the flames have orange flickering amongst the blue, it will go off - pilot and all - in a minute or less. If the flames are all blue, it will stay on and cycle normally. I've noticed the orange flames and the heater shutting itself off more frequently when it's cold outside (below 40ºF) than if it's mild (above 50ºF), and for the past few days it hasn't been above 30ºF so it won't stay on at all. It's fairly new, used only three months altogether, but it has no value as furniture or art. Is this problem something more than the heater? Thank you for your time!