Someone at the thrift store must enjoy grouping dishes by color, because these pieces were together on a shelf, even though they are not a set. The white and yellow cup is from Japan, while the two solid yellow cups are from the USA. The little cream pitcher might be from the same maker as the yellow cups, but maybe not.
At any rate, they look nice with the yellow teapot I found at the antique store a few months ago.
And the tatted doily they're sitting on will look nice on a tea tray.