Project Health Formula

Question on how to do the following in Excel.  

I have the following fields:

• Cost
• Schedule
• Scope 
• Overall Project Health.  

Cost, Schedule and Scope can have the following values each:

• Red
• Yellow
• Green

The formula I am trying to create is for Overall Project Health

• If Cost, Scope and Schedule = Green, Overall Project Health = Green (all MUST be Green)
• If any of Cost or Scope or Schedule = Yellow, Overall Project Health = Yellow
• If any of Cost or Scope or Schedule = Red, Overall Project Health = Red

So in the scenario above, if for example, Cost - Green, Scope = Yellow and Schedule = Green, Overall Project Health = Yellow

 or

Cost = Red, Scope = Green and Schedule = Yellow, Overall Project Health = Red.