If you want to change the color of the lines based on a colormap, you can apply those colors to the "ColorOrder" property of the axes.
h = plot(rand(5));
cmap = hot(numel(h));
set(gca, 'ColorOrder', cmap)
Alternatively, you can apply the colors to the color handles of line objects,
Note that if your really want to use "hot", you'll end up with yellow and white lines wich are difficult or impossible to see against the default white axis. In that case you can change the axis colors to some other dark color.
set(gca, 'Color', [.2 .2 .2])