One of the most common and useful uses of the drop shadow effect is to make your text stand out or "pop" when contrasted against a picture or color background.
To implement the drop shadow effect, select an object within your Google Slides or Drawings project; then in the menu bar select FORMAT and then finally FORMAT OPTIONS.
Clicking the DROP SHADOW effect will then allow you to change COLOR, TRANSPARENCY, ANGLE, DISTANCE, and BLUR RADIUS. Feel free to play with these settings to achieve your desired effect.
TRANSPARENCY - Specifies the percentage of black you want added for the drop shadow.
ANGLE - Rotates the drop shadow around the object
DISTANCE - Determines how far the drop shadow is offset from the object
BLUR RADIUS - Specifies the distance from the edge of the shadow where you want any blurring to occur.