Initially I thought I could use the same field on both entities, but I want the user to be able to select unlimited values from the reference field limited to the options that could exist in the original field.
In the field settings, I need to have the ability to select a field to reference. When looking at the field instance I'd like to be able to tell which field the value should be compared against. The user should be able to select from all of the possible values of field A and store that selection in field B.
Changed this, as it made it sound like I wanted something similar to node reference
Entity 1: Field A
Entity 2: Field B (Values from Entity 1: Field A stored in Field B)
The goal is to be able to use Field B to find entities having Field A that are the same value
Is there any way to achieve this kind of relationship between fields?