coloring points based on value

I have x & y coordinates of points. Also each point has one of the two values (2,4). I want my point to be blue if value is 2 otherwise red. The way i am doing is taking too much time. Please suggest faster way

for z = 1:N_s
    l = length(P{z});
    a = 1;
    while a <= l
        x = P{z}(a,1); y = P{z}(a,2);
        figure(1)
        p_s = S{z}(a,1);
        if p_s == 2
            plot(x,y,'.', 'Color', colorstring(1)); hold on
        else
            plot(x,y,'.', 'Color', colorstring(2)); hold on
        end
        a = a + 1;
    end
    axis equal; hold on
end

Answer 1

[KSSV]

You need not to use a loop. You can achieve this by getting the required indices and plotting. Check the beow demo example:

x = 1:10 ; 
y = rand(size(x)) ; 
% get values less than 0.5 
idx = y<0.5 ; 
% plot 
figure
hold on
plot(x(idx),y(idx),'.b') 
plot(x(~idx),y(~idx),'.r')

[mukesh bisht]

But in my case color is not based on its x or y value. Each point has a value (2 or 4) in addition to x & y coordinates. Color should be based on the value 2/4

[KSSV]

That is not a problem......you can use index for the value and plot x,y. Let x,y,val be your values.

idx = val==2 ; 
figure
hold on
plot(x(idx),y(idx),'.r')
plot(x(~idx),y(~idx),'.b')

Also have a look on the function gscatter. You can use this function as well.