How can I increase the color of certain pixel value in an intensity image?

I have an intensity image and want to color the pixels which their intensity is above 120. In fact I want to replace pixels who's value is above 120 and i want to increase the color of same image red,green,blue by 10,only for above intensity 120 . How can I do this?

[Walter Roberson]

How can an RGB image be an intensity image?

[Som]

gray image it is

Answer 1

[Walter Roberson]

mask = YourImage > 120;
newImage = YourImage;
newImage(mask) = newImage(mask) + 10;

[Som]

if i want to increase blue by 10 and decrease red by 10,increase green by 20.how can i do?

[Som]

Thanks a lot sir.it's working