Components:

R1=R2=R3= 22K

R4=R5=R6= 1K

D1=D2=D3= 1N4148 or similar

TR1=TR2=TR3= BC237B or similar

DZ1 = zener diode  4.7V 1/4 Watt

DZ1 = zener diode  2.7V 1/4 Watt

DL1=DL2=DL3= led

Transistors are voltage comparators, by changing zener voltage you can change the voltage and therefore the threshold at which the comparator switches, and you can add new comparators.