What's the best way to represent XY plots with color squares, as typified by "shmoo plots"?

i.e. QColor shmoo[x][y];

where: X + Y represent the coordinates of a square, and a color per square can be assigned

These don't appear to be a native plot type -- so how much functionality can be gained by overloading current functionality?

Constraints:

- Axis numbers must be placed in-between grid lines.
- Grid lines bound each square.
- Each square may be a different color.

Examples:

image5224074054341222068.jpg

sram4.jpg