Oil paint is very durable indeed, and expert hands would probably do this job very well. It is more difficult to learn, however, and uses much turpentine, which can easily cause some damage. Dry, the finish is durable and less glossy than oil paint. A high gloss is not usually desirable on clock faces. Now to the secondary colors orange, green, and purple.
Orange goes between red and yellow, green between yellow and blue, and purple between red and blue.
Orange is between red and yellow because if we mix red and yellow we get orange. The same is true of the other secondaries. Green is half yellow and half blue. Purple is half blue and half red. Our purple will be very dark almost black.