Change transparency but only in part of a kernel (i.e. different contrast bands)?

I'm using Matlabs sample code to generate Gabor kernels (shown below).

I want to be able to manipulate the transperancy of the contrast bands to create something like the image attached.

I know I can manipulate the alpha level, but this controls the transperancy for the entire image. Therefore, I'm not sure if it is possible to highlight, say, only the black or grey lines in the Gabor kernel.

g = gabor([5 10],[0 90]);
figure;
subplot(2,2,1)
for p = 1:length(g)
    subplot(2,2,p);
    imshow(real(g(p).SpatialKernel),[]);
    lambda = g(p).Wavelength;
    theta  = g(p).Orientation;
    title(sprintf('Re[h(x,y)], \\lambda = %d, \\theta = %d',lambda,theta));
end
%%
x = imshow(real(g(1).SpatialKernel),[]);
%%