At least some numbers-colors association are not due to synesthesia.

For example, if a person made either of the following two associations, one should not suspect synesthesia.

1 White
2 Red
3 Light green
4 Crimson
5 Yellow
6 Dark green
7 Black
8 Brown
9 Blue
10 Orange


1 Red
2 Yellow
3 Green
4 Brown
5 Blue
6 Pink
7 Black