Haven't seen the 'sunset rainbow' you're mentioning but on two
occasions, before and after making a night dive at Makua, I have
been treated to a "moonbow."
 
Once was from a setting first quarter moon shining into some
tradewind showers over the valley of Makua. The other was a rising
last quarter moon shining on some showers which were blowing out
onto the Pacific after favoring me with a fresh-water washdown.
 
Nice!
 
Aloha,
 
makuabob