Question

a tool that samples colors in order to set colors whether for different objects, foreground, or background. ○ eyedropper ○ rainbow ○ color stream ○ color swatch

Explanation:

The Eyedropper tool is specifically designed to sample colors from an image or screen. It can then be used to set those sampled colors for various elements like different objects, foreground, or background. A rainbow is a natural phenomenon of light dispersion. Color Stream is not a standard tool with this specific color - sampling and setting function. A color swatch is a sample of color but not a tool for sampling and setting colors in the described way.

Answer:

Eyedropper