c# picture grid and pixel

[C# Programming]

Hello, i'm trying to write a quick mock up system so my mother knows the colours of pictures when she cross stitches. I would like to import a picture overlay a grid i think it's 1mm boxes then be able to pick up the pixel or rgb colour. I've written the code to convert the colours to pattern chart colours but i was wondering if it was possible to overlay a grid then tell the colour of each square so i can easily convert it. I heard c# has a grid function as standard however i'm struggle to find it or use it