Creating colours for given points on a graph

I want a graph of t by n (t ranges from 0.1 to 100 and n from 0.01 to 100). And I have calculated roots between these ranges for an equation. I need to plot a gray or dark colour for positive root values and just white for negative root values but I am not sure how to do this. Can anyone help? I am relatively new to matlab

[Walter Roberson]

Do you want a mesh plot or a surface plot or a scatter plot? If you want a mesh or surface plot, then what color should the joining lines or surfaces be? What color should the background be if you want the white values to show up?

[jamie]

I just want the corresponding point to be either given a dark gray colour or white colour and the background to just be white so I can just see two areas (dark gray and white). This will be a scatter plot

Answer 1

[Image Analyst]

One of the arguments to scatter is the color. Make an N by 3 array of doubles in the range of 0-1 which represent the RGB color for each of your elements.