Depicting pebbles can seem like an overwhelming enterprise, especially for the beginning painter. Luckily, there are a few tips and tricks to painting beautifully detailed pebbles easily. You must have white and black paint but beyond that you can use any colour from red to orange to purple when creating your pebbles. Keep in mind however, that the size of your brush will determine how small your pebbles will be. Using acrylic paint will allow you to blend your paints easily but it will also dry quickly.
Identify the angle of the light in your painting. Remember that lighting from above makes pebbles look different than lighting from the side would.
Prepare the background. This can simply be painting the background light green so you can fill it in with grass later, but if you are ambitious, consider using a soft cloth or a sponge to add texture to the background. Keep your light source in mind and shadow the background as necessary. In other words, if the light is coming strait on but from the side, paint the background a darker colour first and layer it with lighter colours to give a multidimensional effect.
Paint circles, ovals and other round forms using your black paint. Only paint the outlines. Paint some overlapping the other so that the effect is "fuller" instead of sparse or flat.
Mix your paint to make the colours you want. You can paint each rock a different colour or try a more uniform look. Keep in mind that all rocks have some degree of variation in shading so if you want a uniform look use lighter and darker shades of the same colour. If you use exactly the same shade the painting will look monotonous.
Paint each pebble one at a time. Use a reference image if you need to and lighten or darken your colours as necessary. To lighten the shade add a tiny amount of white (the amount that will fit on the tip of your brush) to your colour and mix it in. Add more as necessary until you reach the desired shade. Use the same process with black paint to darken the shade. Remember that the lightest shade of each pebble should be facing the same direction, where the light is coming from. Use the darkest shade around the edges (what you originally painted black). The black paint can peek through under the pebbles and give a sense of depth and shadows.
Remember the nature of acrylic paints and add your "luster" effects before it dries. Use a tiny amount of white paint on the side the light source is coming from to make a "sheen". A bit of black on the opposite side creates a three-dimensional shadow effect.