An American pollen color chart is difficult to find. One of the reasons appears to be the size of the area of the United State, considering just the contiguous 48 states, and the number of climate and vegetative zones involved from the northern boreal zone to the subtropical.
Our beekeepers (members of SnoKing Beekeepers Association) keep bees in Western Washington and find that pollen information to suit our cool maritime, temperate zone climate and vegetation can often best be found searching beekeeping in similar regions, such as the United Kingdom or northern Europe.
Another way to find useful information relevant to our area is to select it from a general information. For example, the best list of US pollen sources with color information may be found at https://en.wikipedia.org/w/index.php?title=List_of_pollen_sources&oldid=1097890833 . then by extraction of data from that source, perhaps we can make a more useful pollen color chart. Here's one such attempt pictured:
