Ceri is too young to remember The Water Margin on TV in the UK. I, unfortunately, have it very much impressed on my brain. The actual saying was "Do not despise the snake for having no horns, for who is to say he will not become a dragon?" It did not mention any colour of dragon... so as not to offend no doubt. Perish the thought!
It is actually quite a wise saying. As wise as "Are you only having 2 pints of Tomos Watkin? I'm getting in the next round",