This schematic serves as a color detector. This circuit has three LDR sensors equipped with Red Green Blue (RGB) basic filter. Variable resistors (V1-V3) control the LDR sensor sensitivity. This circuit only uses two types of digital ICs, the And and Not ICs. 8 indicator LEDs represent 8 colours (Red, Green, Blue, Magenta, Yellow, Cyan, Black, and White). Here is the schematic :

Colour Sensor Circuit Schematic Diagram

Components list :
R1-R8 resistors : 1k ohm
R9-R11 resistors : 220k ohm
VR1-VR2 resistors : 10k ohm
IC1-IC3 : CD4073B
IC4-IC5 : CD4069B
LDR1-LDR3 : 5mm LDR
LED1-LED8 : 5mm
9V DC Power supply