I’m not certain what you want.
Try this:
E = 2;
H = 3;
t = linspace(0, 2*pi);
omega = 2;
k = pi/2;
x = ones(size(t));
c = cos(omega*t - k*x);
figure
patch([t fliplr(t)], [c zeros(size(c))], [zeros(size(t)) zeros(size(t))], 'b')
hold on
patch([t fliplr(t)], [zeros(size(t)) zeros(size(t))], [c zeros(size(c))], 'r')
hold off
grid on
view(40, 40)
producing this figure:
