How do I Randomly colour arrows on excel

I have a flowchart in excel made with over a thousand rectangles, and many more arrows connecting them. It can be very difficult to track an arrow from one rectangle to another, as the arrows are all the same colour. It would be great if the arrows we're randomly (random, at least to the human eye) coloured with just a few, dark enough to see, distinct colours. for example, blue, green, red, orange etc..

Question:

Is it possible to code a macro that can colour the arrows as above. If it is, what is it? Or, what is a clever way to go about this?