The software and firmware for the colorimeter can be found in our online repository here https://bitbucket.org/iorodeo/colorimeter/src The firmware for the Arduino is in the "firmware" sub-directory of the project. This will be what you want to modify to add you LCD display. Beyond that it is really up to you add the display you want and modify the firmware correctly.
It looks like the nokia 5110 is 3.3V so you may require a level shifter.
You might look at using the Adafruit PCD8544 Nokia 5110 LCD-library https://github.com/adafruit/Adafruit-PCD8544-Nokia-5110-LCD-library
There is a tutorial here https://learn.adafruit.com/nokia-5110-3310-monochrome-lcd/testing