> but it looks like it's something like "banner divided in yellow (towards the flagpole) and white

https://en.wikipedia.org/wiki/Flag_of_Vatican_City says “A vertical bicolour of gold and white”.

I would have thought that should be gold and silver (https://en.wikipedia.org/wiki/Tincture_(heraldry)), but (https://en.wikipedia.org/wiki/Tincture_(heraldry)#Other_tinc...) “The heraldic scholar A. C. Fox-Davies proposed that, in some circumstances, white should be considered a heraldic colour, distinct from argent”, so who knows? Maybe it is gold and white.

Edit: https://www.vaticanstate.va/it/stato-governo/note-generali/b... says “un drappo bipartito di giallo (verso l’asta) e di bianco”, so the Vatican itself says it’s yellow and white.

(Interestingly, there’s a convention for converting those colors to monochrome: https://en.wikipedia.org/wiki/Tincture_(heraldry)#Monochroma...)