Here are my suggestions.
1.Open the Database manager,goto the "Alerts" database and look for the column "LogMessage".There you need to look for something like this "Interface....for node...has a transmitted utilization of ...which is greater than...." and "Interface....for node...has a transmitted utilization of ...which has dropped from above the...."
Once you track them down,you may run an update query to stop these alerts."Update Alerts set enabled='false' where alertid=*"
2.I don't think you could change colors because there is no such option available in the GUI.
3.I don't think you could add more templates.If I am understanding this correctly in the customize page option,is there a way to add more options than the ones present by default.