A Coloring Structure
    
We will consider a structure for a collection of colors that will provide 
a scheme for designing a web page. 
  
Conditions for a Coloring Scheme Structure
  
 -  Each scheme will have exactly 3 colors.
 
  -  Any two coloring schemes together will use exactly
5 colors.
 
  -  Any two colors determine a unique scheme.
 
  -  There are at least two schemes.
 
 
 Here are two examples: 
Notice that each structure has 7 colors and 7 schemes! 
 
    
 | C | 
  E | 
  G | 
    | 
    | 
  G | 
  B | 
  C | 
 
  
 | B | 
  D | 
  G | 
   
       | 
   
       | 
  G | 
  D | 
  F | 
 
  
 | A | 
  F | 
  G | 
   
       | 
   
       | 
  G | 
  A | 
  E | 
 
  
 | A | 
  D | 
  E | 
   
       | 
   
       | 
  C | 
  E | 
  D | 
 
  
 | B | 
  F | 
  E | 
   
       | 
   
       | 
  D | 
  A | 
  B | 
 
  
 | A | 
  B | 
  C | 
   
       | 
   
       | 
  C | 
  A | 
  F | 
 
  
 | D | 
  F | 
  C | 
   
       | 
   
       | 
  B | 
  F | 
  E | 
 
 
  
  
 
 
The question we have is:
  
Are there any color scheme
stuctures that have more or less than 7 schemes made from 7 colors?
  
That is, is there some 
special relation between these color scheme structures and the number 7?