Consider the example
% placeholder data
x1 = rand(100,1);
x2 = rand(100,1);
y1 = randi([0 81],100,1);
mask = y1<10; % create a mask
% plot the two sets
scatter(x1(mask),x2(mask),50,"og","filled"); hold on
scatter(x1(~mask),x2(~mask),50,"or","filled")
Alternatively, you could use colormapping:
figure
cmap = permute(ind2rgb(mask+1,[1 0 0; 0 1 0]),[1 3 2]);
scatter(x1,x2,50,cmap,"o","filled")
