Indication of mains supply under more conditios - rgb led used - both off: blue, both on: yellow, one on: red/green. The parallel diods and resistors reduce the intensity of other colors agsinst blue. The serial resistor ro red ballances the yellow color. All those 3 resistors are subject to adjust for particular led. Other values are adjusted for h21 of transistors = 300, Vred = 1.8V Vgreen = 2.35 V, Vblue = 2.55 V, Iled = cca 2 mA. Zener diods are not necessary - used only for protection of capacitors, transistors and diods against accidental over-voltage. Increasing the 220nF capacitors to 2uF and more increases the smoothness.
