Why does a sandstone bed vary in color?

The reddish sandstone beds are enriched in iron-bearing minerals which turn red-brown when they oxidize during weathering. In contrast, the whitish sandstone beds are void of iron mineralogy and therefore do not develop the reddish color. read more

Basically the sandstone beds vary in colour because of the presence of other elements such as iron(resulting in the red colour), and the presence of many mafic minerals may be the reason behind the dark colour of sandstones. read more

Of course, sandstone can vary in composition in different locales based on the mineral composition, which affects how sandstone looks and feels. Sandstone is primarily particle sized quartz sand combined with very fine grained minerals, but it’s those added minerals that affect the color of sandstone. read more