As we are computer engineers, from time to time we are asked if we could create a breeding calculator to determine the odds of a foals' colour. It may seem a straight-forward computing query, yet genetics seems to be a science unto its own and could be interpreted in many ways.
Those who know more about breeding than us have created resources online that may assist you. We have scoured the internet for a few references that may assist you to determine foal colouring.
This calculator is quite detailed and allows for entering subtle variances in Mare and Sire colouring: