naming the lines leaves1 and 2 just makes it easier to select them to apply the brush. You need name the colour of the leaf shapes that you use to make a brush.
draw a leaf shape you can leave it the default black if you like. select your leaf shape and open the colour editor and click the name tag and name your colour like I said before I like to use brush.
once you have applied the brush to the lines the leaves should take on the colours of the lines. To change the colours of the leaves you can click on any colour on the colourline or in the case of this tutorial you have the named colours that imported with the fractal if you click on one of them you can edit that named colour to edit your leaves.