Counting objects in an binary image of olympic logo

try this :

% Convert the image from rgb into hsv color space:
hsvImage = rgb2hsv(rgbImage);
% Extract the hue image
h = hsvImage(:,:,1);
% Get the histogram
counts = histcounts(h, 1000);
% Find peaks in the histogram
[peaks, indexes] = findpeaks(counts);
% count the number of peaks
numberOfHues = length(peaks)