This is easy, but you need to use handles if you want the figure to look like the one you show. And also, you have to think of the bar, as the polar plot will have the values on the concentric circles of the polar plot. Anyway, here is the code:
First, some data
% the data
a=0:0.1:2*pi;
b=rand(size(a));
c=0.5*rand(size(a));
Now display it in a figure with polar plot
% create the plots
figure
hold off
polar(a,b,'g-')
hold on
polar(a,c,'r-')
Now add the legend, grab the handle and reposition:
hLegend = legend('a','b','Location','NE');
hLegend.Position = [0.7830 0.8806 0.1036 0.0869];
I would say that the figure looks good so far, but if you want the bar, add it and grab the handles, change the position, the ticks and the labels of the ticks:
% Add the bar, grab handles
hBar = colorbar;
hBar.Position = [ 0.1112 0.1024 0.001 0.8167];
hBar.Ticks = [0.05:0.1:1 ];
hBar.TickLabels = [10 0 -10 -20 -30 -30 -20 -10 0 10 ];
