Rainbow’s

I am doing an art project on natural Phenomenon, I will also be exploring the reaction between potential harmful substances, with natural and vital substances for human’s to survive. I am focusing on rainbows, for example the reaction between oil and water; I need help from a science point of view and thought that this would be the right place to pose my question.
I’m aiming to physically recreate a rainbow, like one which you get from oil and water.
How could I achieve this?
I’ve previously tried by adding little amounts with water spraying the oil as to mimic rain in direct sunlight, but can’t capture the strength of the rainbow which you typically see on a road surface.
Does anyone know why this might be?
And how could I resolve this? Will other materials work better? Or is it the consistency?
Any advice would be much appreciated thank you