/drawdot -ihnr @ <color> <size> <x y> [<x y>...]
Draws a dot using the specified color and size at the x,y co-ordinates. Multiple co-ordinates can be provided.
-i draws in inverse mode. -h highlights the windows icon if it is minimized. -n prevents the display from being updated immediately. This allows you to make changes to the window in the background and then display the results only when you have finished. You can update the display by using any of the /draw commands with only the window name specified. -r indicates that the color is in RGB format. You can use $rgb(N,N,N) to create an RGB value.
/drawdot -h @drawingboard 4 10 15 15
Draws a dot in the window @drawingboard, with a color "4" (from your mIRC's color settings), size of 10 pixels, at the coordinates x = 15, y = 15 (15 pixels from top and 15 pixels from left), and -h highlights the window.
/drawdot -r @drawingboard $rgb(0,255,0) 11 15 15 35 35
Draws 2 dots with a size of 11 pixels in the window, 1 at coordinates x=15,y=15 and second one at x=35,y=35, using -r switch and $rgb() to make the color green in this case.
The whole window can be cleared by using the /clear command, eg. /clear @name. You can also specify the -n switch in /clear to delay the effect as described above.