I would be interested in examining several of the courses at Bethpage State Park further to better understand their original design.
Specifically, I hope Phil reads this and shares his knowledge. The basis I have for comparison is an aerial dated 1935 in the clubhouse, and Bill Quirin's book "America's Linksland". In it, I have read about reports of both the Red and Blue courses being excellent tests of golf. Considering the great terrain, the state of the current Blue course, which, IMO is unexciting nor inspiring to play at best, four courses may have been better than five.
In addition, from the aerial, which I admit is limited in what it can convey, it appears there is more width in playing corridors, there are greater expanses of bunkers, and, more than likely, a greater use of angles in playing the course.
Further, the original Blue course (part of today's Yellow) was reportedly tougher than the Red. It also appears that the natural gully that runs through the Yellow first nine and several holes on today's Blue course was better utilized in the original routing.
On the Red course, for one example, it appears that the 13th hole featured the sandy waste area cutting into the fairway from the right; thus, there were two ways to play the hole; lay up short or go left over several bunkers for a better angle of approach.