beginfig(1);

 %the color scheme
 def r = 0.4*white enddef;
 def y = 0.7*white enddef;
 def b = 1*white enddef;
 def blk = .1*white enddef;

 u=1.25in; %overall scale
 s=.5in; %offset between squares
 k=1pt; %thickness of the black lines
 
 %macro to draw the square
 def colsquare(expr xshift,yshift, cola, colb, colc, cold) =
  fill (0,0)--(0,u)--(0.5u,0.5u)--(0,0)--cycle %
       shifted (xshift*(u+s),yshift*(u+s)) withcolor cola;
  fill (0,u)--(u,u)--(0.5u,0.5u)--(0,u)--cycle %
       shifted (xshift*(u+s),yshift*(u+s)) withcolor colb;
  fill (u,u)--(u,0)--(0.5u,0.5u)--(u,u)--cycle %
       shifted (xshift*(u+s),yshift*(u+s)) withcolor colc;
  fill (u,0)--(0,0)--(0.5u,0.5u)--(u,0)--cycle shifted %
       (xshift*(u+s),yshift*(u+s)) withcolor cold;
  draw (0,0) shifted (xshift*(u+s),yshift*(u+s))--%
       (0,u) shifted (xshift*(u+s),yshift*(u+s))--%
       (u,u) shifted (xshift*(u+s),yshift*(u+s))--%
       (u,0) shifted (xshift*(u+s),yshift*(u+s))--%
       (0,0) shifted (xshift*(u+s),yshift*(u+s))--cycle %
       withcolor blk withpen pencircle scaled 2k;
  draw (0,0) shifted (xshift*(u+s),yshift*(u+s))--%
       (u,u) shifted (xshift*(u+s),yshift*(u+s)) %
       withcolor blk withpen pencircle scaled k;
  draw (0,u) shifted (xshift*(u+s),yshift*(u+s))--%
       (u,0) shifted (xshift*(u+s),yshift*(u+s)) %
       withcolor blk withpen pencircle scaled k;
 enddef;

 %first row
 colsquare(0,0,b,y,r,b);
 colsquare(1,0,r,r,r,b);
 colsquare(2,0,r,y,y,b);
 colsquare(3,0,y,b,b,b);

 %second row
 colsquare(0,1,b,y,b,y);
 colsquare(1,1,b,r,b,r);
 colsquare(2,1,b,r,b,y);
 colsquare(3,1,b,b,b,b);
 
 %third row
 colsquare(0,2,b,y,y,y);
 colsquare(1,2,y,y,r,r);
 colsquare(2,2,r,r,r,r);
 colsquare(3,2,r,y,b,b);

 %fourth row
 colsquare(0,3,b,y,r,y);
 colsquare(1,3,r,y,y,y);
 colsquare(2,3,y,r,r,r);
 colsquare(3,3,r,r,b,y);
 
 %fifth row
 colsquare(0,4,b,b,y,y);
 colsquare(1,4,y,y,y,y);
 colsquare(2,4,y,r,y,r);
 colsquare(3,4,y,r,b,r);

 %sixth row
 colsquare(0,5,b,b,r,b);
 colsquare(1,5,r,b,y,y);
 colsquare(2,5,y,b,r,r);
 colsquare(3,5,r,b,b,r);

 endfig;