Gradient color matching refers to the art of combining colors in a way that creates a smooth transition or a harmonious blend. The '6 kinds of gradient color matching chart' likely provides visual examples of six different types of gradient color combinations. These might include linear gradients, radial gradients, diagonal gradients, and various color blending techniques such as complementary colors, analogous colors, and monochromatic shades. Such charts are commonly used in design, art, and digital media to understand and apply color theory effectively.