Ok so i am making some colour orientated posters as a gift for someone... (there are 4 of them each one has 4 pics on it and each poster has its own colour one is red, blue, green, yellow) so what im looking for is ideas of things to take for the colours blue and yellow... im looking for some stuff that is really creative so not things like the sky or a school bus... i almost have the colour yellow covered because of fall colours but i am completely stumped for blue

if anyone has some ideas it would be a great help