Red is not a standard Silkie colour and many, including mine are a little too buff to be the best. The colour should be a deep rich shade or red similar to that of a Rhode Island.
The genetics of the red Silkie:
Buff and red Silkies are both either e^b or E^Wh. e^b birds are more likely to have black in the plumage and darker combs. E^Wh birds are more likely to have clearer plumage and lighter combs. Blacks can be either E, E^R or e^b based.
The red Silkie still has black skin and bones, blue earlobes, and five toes on each foot, whereas most chickens only have four.
So what is the difference between a red Silkie and a buff Silkie?
Red Silkies should be darker but I have see quite a few, including some of my own, that could be called dark buff. It is also common for early generations of red Silkies to have a measure of normal feathering, especially on the wings.
Below: Red Silkies are pictured below with Buff Silkies for comparison. T%he top bird is a buff Silkie hen and the bottom picture is a red Silkie, albeit too light in colour.
Buff colouring in chickens is a shade of orange yellow with a rich golden cast.