Having Arduino read number from file on computer then translate it into color

I'm currently working to on project my workplace. I'm trying to make an ambient color cube that will sit on my desk and change from green to red through the spectrum as we get more emails from customers, say 1 email would be bright green, 500 would be yellow and 1000 or more would be red. I would like it to change fluidly through the spectrum as the number gets higher.

I got API access from the company we use to receive customer emails and can query the current number of unresolved cases we have and write it to a text file.

Basically I'm looking for a solution for getting the Arduino to read and translate that number into a color to output to a piranha LED. I'm not sure the logistics of getting an Arduino to do this. Do I need to write a Python script that pushes that number to the Arduino, and an Arduino script that translates the number to a color and outputs that color? Or can the Arduino go and and grab the data and translate it?

Any help would be much appreciated.

Yes one way would have the arduino getting pushed with data, e.g. from python.
If the API isn’t to cumbersome to access and use, and if you have an extra network outlet you could get an ethernet shield (or ethernet arduino) and let it do all the job, so powering off/restarting your PC won’t interfere.

There is also a project for extending the arduino's reach within the PC via some coding, http://arduino.cc/playground/Interfacing/GoBetwino

GoBetwino is kind of a "genreric proxy" for Arduino. It's a program running on a PC (Windows only), that will act on behalf of Arduino and do some of the things that Arduino can't do on its own.

Sound like this could read a file on the PC on behalf of the arduino so it gets the information (number of unanswered e-mails). I haven't tested it myself and I noted that the source code is quite old. Perhaps isn't updated for never Arduino and need some polishing.

GoBetwino can do it. It can ask the computer to send a specific line from a txt file.