Purple-blue gradient poster design refers to the creation of a visual design using a smooth transition between purple and blue colors. This technique is often used in graphic design to convey a sense of calm, creativity, or transition. In poster design, such gradients can enhance the overall aesthetic appeal and convey a specific mood or theme. Techniques for creating purple-blue gradients include using software like Adobe Photoshop or Illustrator, where tools like the Gradient tool are employed to blend the colors seamlessly.