Multiple polar plots on same figure - different colors for each plot?

I am trying to produce several polar plots on the same graph, using a loop. Each plot will have a different color.i.e. one color per iteration. However, I am having problems with the color specification.

Here is what I have:

for j = 1:10
   .
   .
   .
   a=polar(x,y,color)
   legend(a)
end

Questions:
a. Is there a way to specify a separate color for each iteration of the loop?
b. Is there a way to display a legend showing all the colors in the figure?