Not 100% sure of what you're trying to achieve, but perhaps this function could help you. More specifically: cursor(image, x, y)

Thanks for the feedback.

I wish to change to colour of the cursor dependant on what colour is selected from a colour picker.  

So if the user picks red, I want the colour of the cursor to change to red so they can see they will be painting with a red brush.

Hope this helps?

I can't create a custom icon for every size and every colour selectable - this would mean in excess of 1000 cursors

In addition to all the above suggestions, here is a code example of using a SVG as a cursor and then custom coloring it in Processing. Just threw this together quickly, so there may be better ways of doing it. Put the SVG in the data folder of your sketch.

Code:

PShape cursorsvg;
PGraphics cursorcolored;

void setup() {
  size(500,500);
  background(0);

  // load the custom cursor shape from svg
  cursorsvg = loadShape("cursor.svg");

  // create PGraphic for changing colors
  cursorcolored = createGraphics(30, 30, JAVA2D);
}

void draw() {

  // draw the svg with custom colors to PGraphic
  // this is just an example with different fill and stroke
  // when the mouse goes either left or right from the center
  cursorcolored.beginDraw();
    cursorsvg.disableStyle();
    if (mouseX < width/2)
    {cursorcolored.fill(200, 0, 0);cursorcolored.stroke(255);}
    if (mouseX >= width/2)
    {cursorcolored.fill(0,0,200);cursorcolored.stroke(255,255,0);}
    cursorcolored.shape(cursorsvg, 0, 0);
  cursorcolored.endDraw();

  // use the PGraphic as an image for cursor function
  cursor(cursorcolored);
}