Red 1.8 mm LEDs

 
Red LEDs are electron hogs. They will always be the first to glow and even prevent other LEDs from illuminating.
 
Red 1.8 mm LED and White 1.8 mm LED powered by 3V coin cell battery CR2032
 
When designing your circuits be sure to isolate the red LEDs from other colors otherwise you’ll have a darkwad in the final design.
 
read more on LEDs at wikipedia