In the early 1980s, IBM developed the Color/Graphics Adapter for its new IBM PC, defining 16 colors via a 4-bit binary code. The evolution of color 6, referred to as brown, raised questions on how to achieve the desired shade. Amdek monitors needed an upgrade to display 16 colors, as initially, they could only show 8. The introduction of the IBM 5153 established brown as the standard for color 6, despite variations in other IBM models. Sierra’s RGB conversion algorithms for games like Adventure in Serenia faced challenges as brown evolved, but Tandy monitors continued to show a consistent 50% brown. Notably, Tandy monitors did not display brown colors as effectively when paired with non-Tandy graphics adapters, leading to visible color clashes.
http://nerdlypleasures.blogspot.com/2023/03/the-saga-of-color-brown-in-early-years.html