Strengthen the screw which connects the faucet. If the leak continues, replace the body.
Change body of faucet
Make sure that the water flow taps under the sink are open, clean the water softener. If it's a pull out faucet, remove the spray and reinsert it to its place.
Clean or change the water softener, change the rubber seal.
Make sure there is no leak in the pipes connected to the faucet, if the leak is from the connection- gently strengthen the connection. If the leak is from one of the accessories- replace it. If the leak source is from above the sink, make sure that the rubber seal is in place and the bottom screw is tight.
Remove the blue/red mark and tighten the screw
Change or clean the water aerator. If you are using a pull out faucet, take out the spray clean it and return it to its correct place.
Strengthen the connection between the spray and the pipe. If the leak continues, replace the rubber seal.
Reinforce the screw on the bottom of the faucet.