The Green Skin Colour is a vanity reward from 30 or 35 day RuneScape Game Cards from the 20 October to 4 November 2011 or by purchasing the gold membership package between 20 December 2012 and 31 January 2013. This is the third reward which can only be obtained by paying real world money e.g. Dollars and Pounds (after the Flagstaff of festivities and the Ornate katana) to be released and the fourth to be announced (after the RuneFest Hood). Once you obtain the benefit, it permanently unlocks the ability to change your skin colour to green. You can change freely between normal/green skin by speaking to the Make-over Mage or via Diango's holiday item interface. Once you have obtained the ability to have green skin, the option will always be there for you.
Note: You will not receive this reward from purchasing a 90 day card.
Not only did players criticise the green skin for the same reasons as the flagstaff and katana, players complained that green skin can only be obtained via game cards rather than using the automatically-renewing credit/debit card payments.