Schmincke Watercolours [link] Reds #349 and #351 Yellow #216 Raw Sienna #660 Very similar to Ochre, but less opaque. You can use Ochre instead. Ultramarine finest #494
Skin tones can be mixed by any combination of red, yellow and blue.
If you only want to use a single very diluted colour you can try Cadmium Red light or Burnt Sienna. They both give satisfactory hues when you add lots of water.
Some people like to use Naples Yellow deep as a skin colour. I'm not overly fond of it because it usually has white in it, and therefore lifts very easily from the paper when rewetted.
Howver that tone is nice to use in mixed media, if you just need a layer of watercolours and continue with pastels or coloured pencils.
If you want to depict darker skin, you can use Burnt Sienna with the addition of some blues or greens. Just try out various combinations.
Mixing white to reds or browns will give you a generic skin tone that you can paint in a single layer. It's difficult to paint over such a layer because the white allows the layer to lift too easily, and therefore creates a blotchy surface.