How to extract red and yellow tones from RGB images using Matlab

Does anybody know which code should I implement, using Matlab Image
Processing Toolbox, to extract separately the red and yellow tones from an
RGB image, making all other pixels black?
Then I need to threshold the two image obtained, the reds one and the
yellows one, to put them in binary mode and then reconstruct only one image
from the two binary images.
I have this practical problem: I have some frames in JPEG format, taken from
a video file, that contain red and yellow glass microbeads. The background
is blue. I need to extract only red and only yellow microbeads,
respectively, from the images, in such a way to perform certain operation,
like concentration measures in some areas of the images.
Does anybody know also how to obtain a "pixelate" effect (typical of
video-editing softwares like Sony Vegas) for the RGB images in Matlab?
Thanks in advance.


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