ya with khakis i usually wear boxers for that very reason
I have an older pair of Levis Dockers that are very light tan in color. When I bought them, they were one of 5 pair that I bought for my first office job. I wore briefs back then, and you could see the lines of my underwear easily. If the briefs were white, you could even see the seams of the front fly though the fabric. It didn't concern me much; I thought it was hot.
When I switched to boxers 5 years ago, one day I wore those pants to shop at the local nursery. I had to laugh as very little was left to the imagination. It was fun to look at all the plants and flowers while my limp dick was dangling down my right leg. I got absorbed with the flowers and really didn't pay attention as to whether or not anyone noticed.