I was able to do it by making a colorbar 'south' of the 2nd subplot, then changing the position.
So, problem solved, but if anyone knows how to flip the x & y axes of a colorbar without setting the 'location' to 'south' or 'north', that'd be appreciated.
myfig=figure;
subplot(1,3,1);
sp1=plot(1,1,'o', 'markersize', 40, 'markerfacecolor', 'b');
set(gca, 'visible', 'off');
subplot(1,3,2);
sp2=plot(1,1,'o', 'markersize', 40, 'markerfacecolor', 'g');
set(gca, 'visible', 'off')
colbar=colorbar('Location', 'south', 'Position', [.25 .1 .5 .05]);
subplot(1,3,3);
sp3=plot(1,1,'o', 'markersize', 40, 'markerfacecolor', 'r');
set(gca, 'visible', 'off')