Red and gray, flat design

Quick answer：

Flat design is a visual style that emphasizes simplicity and minimalism, often using solid, flat colors like red and gray. It gained popularity in the early 2010s and is characterized by the use of large blocks of color, simple shapes, and clean typography. Red and gray, as part of the color palette, can evoke a range of emotions, from passion and energy (red) to stability and sophistication (gray). In design, these colors are used to create balance and emphasis, often in interfaces and graphic designs.