>What is yellow brick?
During the Middle Ages, yellow bricks were prevalent in Europe's architectural landscape, frequently employed in the construction of medieval structures such as castles, churches, and cathedrals. The vibrant hue of these bricks added a touch of warmth and character to the majestic and enduring buildings of that era.
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Still popular today, yellow bricks are an excellent insulator; they’re, ideal for use in areas with extreme temperatures. Their distinctive hue is derived from iron oxide pigments. Yellow bricks exhibit excellent durability, withstanding weathering and erosion over time. Additionally, they are typically resistant to fire, offering enhanced safety in buildings. They also have a high resistance to moisture and insects.
https://www.modularclayproducts.co.uk/news/yellow-bricks/
London stock brick is the type of handmade brick which was used for the majority of building work in London and South East England until the growth in the use of Flettons and other machine-made bricks in the early 20th century. Its distinctive yellow colour is due to the addition of chalk.
https://en.wikipedia.org/wiki/London_stock_brick