Horse Chestnuts, or “conkers” are always a welcome sight and I look forward to painting them at this time of year as they are so evocative of the change in seasons. You would think that they would all be the same size and shape, but I have yet to see two identical.
For the body of the chestnuts I use combinations of Yellow Ochre, Burnt Sienna and Violet (either Winsor violet or a mixture of French Ultramarine and Permanent Alizarin Crimson). If the chestnut is still bright and shiny I use a brighter yellow. As for the bits on top I make very light washes of mostly the same colours and let them mix together when wet and then go back in later with a few darker washes.
At one time, children used to drill a hole through them and attach them to a piece of string and then bash them against each other’s to see whose Chestnut would “conker”the rest. I tried to keep some of mine in good condition as I regarded them more as lucky mascots rather than weapons.