Dynamically add plane with on the fly generated texture

For a tower defence game I actually devellop I need the abillity to add an additionally plane with a texture image that can modified every second.

Here the steps I need, and whats already implemented.

  1. Spawn a enemy every x seconds - OK
  2. Add a plane attached to the enemy - Actually I spawn a named Plane defined in Blender and set the enemy as parent. But all Planes have the same texture. How can I generate a new texture for every plane?
  3. Set plane as billboard - OK (Found an example that should work)
  4. Paint on the plane - Need to paint on the image texture. Is there a setPixel/setTexel to set the color at a given Pixel/Texel of the image texture?