Yellow and red china paints are more difficult to work with than most colours. Basically there are two types of yellows and reds, the cadmium based ones, which are brighter coloured, and the iron based reds which are duller and more brownish.
The cadmium colours can only be mixed with each other, Held has a great selection, and a fact sheet on using them.
The iron reds are also somewhat problematic as some yellows will fire out red if they are mixed together, and this is often difficult to rectify as the red often continues to fire out when you try to paint it again. So it’s best to test fire mixing your iron reds and yellows to see which ones work best, and at what temperature. Usually a lower fire of 750C will help prevent the colours firing out too much, and also reds can turn brown if they are fired too high.
You can see that most of the reds with some yellows have almost all fired out at 800 C. But at 750 C the results are better.
There is another way of obtaining red, used by the factory artists like the Worcester fruit painters. This method uses a yellow such as egg yolk, fired, then followed by a gold based colour like maroon painted over it and fired.