The stamp which immediately came into mind, because it shows much yellow and even more orange, is this painting by famous painter Mark Rothko:

Pretty orange backgrounds are shown in the following two stamps, both happen to connect two countries:
The Monaco and Morrocan flag on this joint issue stamp from Morocco, and a lot of orange under the book:

From Thailand, orange behind a mailbox from Myanmar:

Almost monochromatic are these two stamps, issued on a ten stamp sheet in honour of Dutch letter writers:

The man pictured is Leo Vroman (1915-2014), a Dutch-American writer, hematologist (the book I've read is an autobiography, also about blood), poet, illustrator.
Finally a stamp which I like to share, is this one from Spain, showing a dear object. Which raises the question: is it orange or is it yellow?!

See more stamps on this theme on and via this Sunday's Sunday Stamps!
Great selection of stamps - the Rothko is a personal favorite.
BeantwoordenVerwijderenI guessed so :D
VerwijderenA print of this stamp is hanging in my living room - the colors are bright and full of energy.
VerwijderenGreat stamps! The top one is my favorite, really perfect for the theme
BeantwoordenVerwijderenI love your selection. I didn't thought of that stamp (issued both by Monaco and Morocco), but it's really orange.
BeantwoordenVerwijderenI can hear that Spanish guitar - it's yellow to me.
BeantwoordenVerwijderen