It was important for KITCHEN to stay true to the authentic appearance of stained-glass windows, so the colour palettes of each window were limited, in order to refrain from cluttering them with too many bold colours. Each window consisted of colours that highlighted and represented each house.
For example:
Stark: Cold greys, Browns, Cold tones (Weirwood tree needs the iconic red foliage) Lannister: Gold (Orange), Red, Greens for the Sept of Baelor explosion