Try this:
x = 0:10:90; % Create Data
G1 = [-1 -2 -3 -4 -5 -7 -9 -11 -12 -13]; % Create Data
G2 = [1 1 2 2 2 2 2 2 2 2]; % Create Data
figure
plot(x, G2)
axis([0 100 -15 5])
hold on
plot(x, G1)
patch([x fliplr(x)], [G1 min(ylim)*ones(size(G1))], 'r') % Below Lower Curve
patch([x fliplr(x)], [G2 max(ylim)*ones(size(G2))], 'r') % Above Upper Curve
hold off
grid
Experiment to get the result you want.
