Create color filled cirlcle to dxf file

Hi, I'm trying to develop a script to create a colour filled circle to a DXF file. For example, I'm thinking of a circle with a known radius and with different values for coordinates (X and Y) and a Z value. This Z value should be related to a colour (for example, a colormap). What should I do?

One option could be:

fullname='test_1.dxf';
fid=fopen(fullname,'w');
fprintf(fid,'CIRCLE\n');
fprintf(fid,'0,0\n');      %Coordinates for center
fprintf(fid,'1\n');        %Radius
fclose(fid);

But it doesn't work. Moreover is missing the filled colour depending on a Z value. What should I do?