Dear Benjamin,
The Ping color code uses a number of different assumptions, and don't necessarily result in a color matching a lie angle. The other assumptions are stance, hand position and stroke style, but Ping is not very clear on the website how these factors translate to color code.
The Ping Color code has black for standard, and in the flatter direction runs red, orange, brown, gold, and in the more upright direction runs blue, green, white, gray, burgundy.
See
Ping Putter fitting -- static fitting for Specify Putters.
Looking only at their putter fitting gauge, the 73 degrees you calculate would be 2 degrees upright more than standard of 71 degrees. According to the gauge, 73 degrees would then be "green."
A flatter lie would be an angle less than 71 degrees, and this would be red or yellow on the gauge.
If the Ping folks are telling you your color is "flatter" than standard, and their standard is the usual 71 degrees, then that is not the same as you measure at 73.1, but must be due to one of the assumptions Ping makes about your stance, hands or stroke type.
Personally, I doubt if their assumptions are based on good stroke technique. I would like to know more about their assumptions.
Cheers!
Geoff Mangum
Putting Theorist and Instructor
Geoff Mangum's PuttingZone
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