Critical Path Colour Code Arrows

Hi My Names is chris and i have been trying to work out how to change the colour of the arrows based on the critical path,

basically i require the arrows to turn red when to show which activity is going to take the most amount of time through the sequence using the earliest finish date as my datum.

please see attached what I have so far, is there anyone that may have an example available for me to duplicate.

Please can anyone help Thanks