My 4 month old has diarrhea yellow in color,he is constantly putting his hand's in his mouth showing signs of teething?

Likely nothing to be: concerned about. Stool patterns vary greatly in infants, and yellow colored stool is not concerning. As long as you infant is drinking/feeding well, there is no need to change anything for mild-moderate diarrhea. As long as he's active, playful and urinating normally, you don't have to worry about dehydration. If it continues more than a week, worsens or bloody, you should contact your doctor.

Anything else?: Well, babies like to chew on their hands at a certain point. Could be early signs of teething or it could just be that he's found his hands. Trust me, for months, everything he "finds" he's going to try to put in his mouth. Teething doesn't really cause diarrhea per se. If he's taking his bottle well, peeing normal amounts it's okay to watch but if the diarrhea persists he needs to see his doc.

Teething: He may be teething at 4 months. Signs of teething are drooling and chewing on things, and sometimes crankiness. With babies everything goes into the mouth So this is not a good indication of teething.