MATLAB: Why does the green in RGB come out yellow

rgb image

i want to use the following code to demonstrate what RGB is but somehow the green comes yellow. anyone knows why is that?
x=-1:.01:1
y=-1:.01:1
[X,Y]=meshgrid(x,y);
Z=sqrt(X.^2+Y.^2);
Z(Z>1)=1;
R=ones(330,330);
G=ones(330,330);
B=ones(330,330);
R(1:201,1:201)=Z;
G(76:276,76:276)=Z;
B(1:201,126:326)=Z;
img=cat(3,R,G,B);
h=image(img)
thanks in advance yair

Best Answer

For all three colors, you are not getting RGB, but the complementary colors cyan,magenta,yellow.
Here's RGB corrected, but with a black background:
x=-1:.01:1;
y=-1:.01:1;
[X,Y]=meshgrid(x,y);
Z=sqrt(X.^2+Y.^2);
Z(Z>1)=1;
R=zeros(330,330);
G=zeros(330,330);
B=zeros(330,330);
R(1:201,1:201)   = 1-Z;
G(76:276,76:276) = 1-Z;
B(1:201,126:326) = 1-Z;
figure
img=cat(3,R,G,B);
h=image(img)
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