I second that.  I play on courses with big, 100 year old cotton woods.  Finding a ball can be hell under a blanket of white.  Not to mention all the leaves in the fall.  All I've played lately is the yellow NXT.

My biggest factor is the surroundings.  I've used yellow in the summertime, but depending on the quanitity of yellow and brown leaves on the course, I may play white in the fall. 

In looking at the marketing of balls, Titleist now supplies 8 product lines including yellow.  The 2 yellow lines match up with the mature golfers.  Moving to 10 for ProV1 and ProV1x creates shelf space issues for retailers and especially golf shops.  It is a conundrum to show ads that average players (read older and/or female) gain benefit with ProV's but not market an optic option.  It is easy to not have an optic ball if your target market is limited to players with driver speeds in excess of 95 and single digit handicaps.

I get about 215-225 max on a drive, and can't follow a white ball that far without really good contrast in the background.  I can see an optic ball that far.  How many NXT Tour-S buyers would move up to a ProV if optic was the option to DT Solo?

Not to long ago there was a discussion about this.  I was against it, but after this weekend when I tried out a NXT Tour S in yellow i bacame a fan.  However, Mike came into say that there were no current plans on making them in yellow, but maybe sometime in the future we'll see them.  Like you said, you can't find the white ones this time of year with all the leaves!