How can I make gray or black color in circle?

As the following source, I made ring including some colors..

But I can't get black or gray color.

How can I make gray or black color in circle?

By which data can color affected?

%# define the ring
phi = linspace(0,2*pi,360);
innerRim = [cos(phi)',sin(phi)'];
outerRim = [cos(phi)',sin(phi)']*1.1;

xRing = [outerRim(:,1),innerRim(:,1),innerRim([2:end,1],1),outerRim([2:end,1],1)]';
yRing = [outerRim(:,2),innerRim(:,2),innerRim([2:end,1],2),outerRim([2:end,2],2)]';

%# create some data. 0 for black 0.5 for gray. 
%# RingData has a value for each degree
ringData = ones(1,360);
ringData(1:40) =0.9;
ringData(40:80) = 0.8;
ringData(80:120) =0.7;
ringData(120:160) = 0.6;
ringData(160:200) = 0.4;
ringData(200:240) = 0.3;
ringData(240:280) = 0.2;
ringData(280:320) = 0.1;
ringData(320:360) = 0;

%# plot the ring
%# for an outer ring, add 1 to xRing, yRing
figure
patch(xRing,yRing,ringData, 'Edgecolor','none');

set(gca,'cLim',[0 1]);
axis square
 axis off
set(gcf,'color','w');

Answer 1

[Image Analyst]

Add this code to the end of yours:

numberOfGrayLevels = 256; % from 1 to 256.
colormap(gray(numberOfGrayLevels));
colorbar;

[Image Analyst]

Haksun's "Answer" moved here since it's a reply to me rather than an answer to the original question.

Thank you for your reply.

And, could I get another color including RGB?

For example I'd like to get [3 17 34] colored dark blue in circle.

Again I really appreciate your concern.

[Image Analyst]

Yes, you can make up a custom colormap. For example you can say

colorMap = gray(256);

and if you want values of 30 to be [3 17 34] , just do

colorMap(31,:) = [3 17 34];

See caxis() to see how you can assign specific values of your data to row 1 and row 256 of your colormap.