What do the different coloured dots on microswitches mean?
Claims from various sellers seem to indicate that the D2FC-xxx switches are mostly physically interchangeable, but with subtle differences in contact alloy, lifetime, country of manufacture and feel, as indicated by the operator color.
Rated lifetime varies from 500x10^4 to 2000x10^4 (20 million) operations.
Edit: Mechanical drawing page from datasheet linked in above:

Chances are good Omron is the original manufacturer, and other similar switches from Taiwan etc. companies are copies.