Noise/Spots
 
 

As the function name already states, this function adds colored Spots to the texture.

Each Elements Count step increases the number of spots by 10. The Size value defines the size of the spots (in percent) relative to the texture's smaller side.

You can see in Image 2 that the edges of a spot are irregular. Decrease the Turbulence value to get smoother spots.

If you set the Amplify value to 0, there will be no transparency gradient from a spot's center to its edge.