After viewing many 1869 $1 Treasury Notes (Rainbow notes) on eBay, it appears that there are actually 2 different types.
One type seems to have much bluer paper than the other. The bluer paper variety is much more beautiful than the other, and really earns its "Rainbow" nickname. The other variety is much more drab looking.
I've tried finding documentation about these two different types, but I cannot find anything.
Can anyone help me out?