The Pollen Loads of the Honey Bee by Dorothy Hodges is perhaps
a clasic for pollen colours and
Pollen Loads, A colour guide to pollen loads of the honey bee
by Willam Kirk.
Both these excelent books are available from the IBRA
However, I must add that colour is very unreliable in determining
plant source.
Have Fun
Regards
Durk Ellison
e-mail: [log in to unmask]