Why is paper generally white and pens are generally blue or black?

Paper is generally white because the brightness enhances readability and provides a neutral background for text and images, making them easier to see. Blue and black pens are commonly used because these colors offer strong contrast against white paper, ensuring that writing is clear and legible. Additionally, blue ink is often perceived as less formal than black, making it suitable for various contexts. Together, these choices optimize visibility and functionality in writing.