The simple solution is to feed the child optimally. This includes; Increasing frequency of feeds, Increasing volume of feeds, Increasing the duration of breastfeeding so that the child would be getting the more rich "hind milk" [see my article on "Breastfed But Starved"]. If it is a child that has been weaned, care should be taken to identify the types of food the child likes eating.Drugs are not neccessary ! Even if diarrhea is the cause, oral drip, and Zinc, are enough.

Starvation isn't the only cause of greenish stools. Some forms of diarrhoea can also cause a similar thing. This is because, in diarrhoea diseases, there is intestinal hurry, with drastic reduction of intestinal transit time. In simple language, faeces moves through quickly, giving little time for conversion of the greenish coloured Bilirubin to the brownish Stercobilin.
The first stool every baby passes, meconium, is also greenish in colour, for the obvious reason that he/she is yet to feed.
Occasional passage of a greenish stool, especially if bulky, and the child is not losing weight, may also be normal.
Lactose intolerance, and milk allergy, may also cause it. In these cases, the child may be fussy, and irritable as well. In the former, there may also be bloating, and excessive passage of gas.

Greenish coloured stools, also so-called "starvation stools," could be an indicator that a child is not being fed well; that he is starving.
This is so as, suboptimal feeding makes small volumes of food materials to be present in the intestine. Most of these would be absorbed by the body, and what would be present at the distal end of the intestine would just be bile, which would then run through, like water in a pipe, without enough time for intestinal flora to convert Bilirubin to Stercobilin. It would then come out as greenish coloured watery stools.