The key components of this proposed pen model includes:                                  
RGB COLOR SENSOR UNIT It senses the colour of the surface to which the pen is made in contact & then decodes the amount of primary color components (RGB) present in that color. This sensing unit is attached to one side of pen & the other side is free for writing purpose.                
CONTROL UNIT
Boundary mapping technique: Once the colour has been detected, it’s time for estimation of required quantity of ink. This is done by toggling the switch present at the sensing side. Once the switch has been toggled, the user has to trace the boundary of the required surface intended for colouring. The data is fed to the mcu where it finds out the greatest distance between two points along the surface being traced. Now the mcu estimates the area of the circle drawn with diameter equal to half of the maximum distance.
Microcontroller Unit: The % of sensed color & area mapped are fed as input to mcu & it generates signals for each RYB ink cartridge to pour out the required quantity of each ink into the pen cylindrical refill, where it gets mixed to form the desired colour.                   
POWER SUPPLY The energy requirement for running of this electronic device is met by harnessing energy from radio waves present all around us.