I don't have this dscatter function, but here is an example of how to do this with imagesc (which is similar enough that you could translate it to your situation). It involves setting the AlphaData property of your image. In the following example, I do so based on if the value is NaN. But you could do it for any value (and thus any colour).
clearvars
close all
clc
% get some data and plot it
z = peaks;
x = 1:size(z,1);
y = 1:size(z,2);
figure
imagesc(x,y,z);
colorbar
% now make some values in z NaN and plot them blank
nanz = z;
nanz(z < 1 & z > -1) = NaN;
figure
I = imagesc(x,y,nanz);
colorbar
% Use the AlphaData property to set the NaN values to blank
I.AlphaData = ones(size(nanz));
I.AlphaData(isnan(nanz)) = 0;
