making greys

[godfather]

I read in articcles people making a colour grey but what do you add to a colour to make it grey. I know about complements added togther make grey but what about making non primary colours grey eg, burnt umber, brown madder etc

 

[megroot]

Talino,

I make my greys with brown madder and titanium white. It is a warm grey.

Marc

 

[godfather]

Sorry I should have been more clear I am wondering what colour(s) to add to any other colour to make a grey tone. Basically is there a rule in colour theory that explains this. Hope this clearer.