Yellow and blue. Nothing new.
That combo has been around for ages. Even St. Peter, that big cheese in Christian religion has always been depicted in yellow and blue. Why? Symbolism? Or was it just that those colours look good together? There is masses of symbolism lurking within Christian paintings. Yellow signifies light, hope and renewal. Blue signifies Heavenly grace and hope. All very fitting for the gatekeeper of Heaven.
But on a materialistic level, yellow and blue do look good together and I like to think that whoever decided St. Peter should always be clad in yellow and blue, sat down with a cup of tea, the colour wheel and had a really good think. He got it SO right (must be the tea). Yellow and blue are complimentary colours (they oppose each other on the colour wheel) and our eyes enjoy resting on the two together and always will. Looking at a painting therefore, we are more likely to notice the figure who floats about in lovely colours. Consequently we are drawn into the action and therefore the message, Christian or otherwise.
Here is the colourful St. Peter, from the Brancacci Chapel, Santa Maria del Carmine, Florence painted by Masaccio in c. 1424. This is a close up shot so he is really obvious, but you can spot him a mile off when looking at the fresco cycle in its beautiful entirety.
Image courtesy of Brancacci Chapel.