I do as follows GoodGuy:
1) fill the desired shape with the color you want it to be close to (in this case #79b449)
2) Make a new layer
3) Make the foreground color a bit darker than the one you used above and the background color a bit lighter (I used something like #4a7228 and #96cb6b respectively - you may have to play around with this depending on the color)
4) Make a selection of the above shape and use the filter Render>Clouds in the new layer
5) Change the blending mode of the layer with the clouds to soft light and the opacity of the layer to something like 80%

Play around with the colors and opacity to get the desired effect.
Hope this answers your question