Flashing dotStar LED
The authors of the library are not fans of the setBrightness() method and advise handling it yourself. 

The following code should do what you want.

#include &lt;Adafruit_DotStar.h&gt;
#include &lt;SPI.h&gt;          

#define NUMPIXELS 60 // This should be the total number of LEDs in your strip 

#define DATAPIN    4
#define CLOCKPIN   5
Adafruit_DotStar strip = Adafruit_DotStar(NUMPIXELS, DATAPIN, CLOCKPIN, DOTSTAR_BRG);  

void setup() 
{
  strip.begin();  
  strip.show();   
}

void loop() 
{

  // loop through each pixel in the control array setting it to the colour mix you want.  
  for (int i=0; i &lt;= NUMPIXELS; i=i+1) {
    strip.setPixelColor(i, 25, 25, 25); // Even 25 on my strip gives reasonably bright flash
  }

  strip.show(); // Then push the control array to the strip 
  delay(1000); // and leave it set for a while

// Then do it again for the 2nd brightness in your scheme

  // loop through each pixel in the control array setting it to off.  
  for (int i=0; i &lt;= NUMPIXELS; i=i+1) {
    strip.setPixelColor(i, 0, 0, 0); 
  }

  strip.show(); // Then push the control array to the strip 
  delay(1000); // and leave it set for a while

}