Blend the colors between two overlapping objects by using blending modes. Blending modes let you vary the ways in which the colors of stacked objects blend.
In the Effects panel, choose a blending mode, such as Normal or Overlay, from the menu.
In the Transparency area of the Effects dialog box, choose a blending mode from the menu.
The blending modes control how the base color, the underlying color in the artwork, interacts with the blend color, the color of the selected object or group of objects. The resulting color is the color resulting from the blend.
If the blend color (light source) is lighter than 50% gray, the artwork is lightened, as if it were dodged. If the blend color is darker than 50% gray, the artwork is darkened, as if it were burned in. Painting with pure black or white produces a distinctly darker or lighter area, but does not result in pure black or white.
If the blend color (light source) is lighter than 50% gray, the artwork is lightened, as if it were screened. This is useful for adding highlights to artwork. If the blend color is darker than 50% gray, the artwork is darkened, as if it were multiplied. This is useful for adding shadows to artwork. Painting with pure black or white results in pure black or white.