While panang curry and red curry pastes both have a rich red colour, there are a couple of key differences: 1) The inclusion of crushed peanuts in the paste gives panang curry a richer, nuttier and earthier flavour than red curry paste.  2) Where red curries often include stock as a liquid in the sauce, panang is usually only cooked with coconut milk, helping the sauce to stay much thicker than other curries.