Exemplo de como usar cores

program calcularmedia;
uses crt;
var a,b,m:real;
    s,n:char;
begin
repeat
textbackground(blue);
clrscr;
textcolor(white);
gotoxy(15,5);
textbackground(red);
window(20,5,52,7);
clrscr; gotoxy(3,2);
write('Digite a primeira nota: '); textbackground ( black);write('     ');
gotoxy(27,2);
read(a);
window(20,5,52,7);
textbackground(red);
clrscr;
gotoxy(3,2);
write('Agora a segunda nota:   '); textbackground ( black);write('     ');
gotoxy(27,2);
read(b);
m:=(a+b)/2;
window(20,5,52,7);
textbackground(black);textcolor(yellow);clrscr;gotoxy(3,2);
write('     Sua nota foi:  ');textcolor(lightblue);write(m:2:1);
window(20,10,52,12);textbackground(magenta);textcolor(lightgreen);
    gotoxy(8,1);
write('Aperte N para sair.');
s:=readkey;
until(s='n');
end.