Are you using OpenGL or just outputting a matrix to a window? In OpenGL you can use a number of ways to draw pixels, look in gl_commands of jit.gl.sketch. When using matrixes, you can always use the setcell message to matrix. But I don't think it's very efficient when you coloring lots and lots of pixels.

thanks. I´m trying to set a pixel with this command "gldrawpixels foo 200 200 2 2" to jit.gl.sketch but I get an error.