The Pacific Star.

   A six pointed star, in the centre the royal cypher GRI VI , within a circlet bearing the title "THE PACIFIC STAR". A  crown is positioned on the circlet at 12 o'clock.
Bars issued (one); Burma.¹
Ribbon emblem issued: (one) a silver rosette denoted the award of the bar. (for when the ribbon alone was worn)

    For the Royal and Merchant Navies² qualification was entry into the Pacific theatre ³ between 8th December 1941 and 2nd September 1945. 
   No time qualification was necessary for the Army and eligibility was entry into the territories that had been invaded by the enemy or the allies. Service in China and Malaya between 8th December 1941 and 15th February1942 also counted.
   Royal Air Force aircrew were eligible on their first operational sortie, ground crew eligible as per the Army.

Notes.
¹ The Pacific Star and Burma Star are mutually exclusive. A bar "Burma" or "Pacific"  was awarded as appropriate instead of the second star.
² For the Navies only;  the 1939-1945 star had to have been earned by six months service prior to becoming eligible
 for the Pacific Star.
³ Pacific theatre = Pacific Ocean, Malaya, China, Indian Ocean, South China Sea. Burma was excluded.

Also see official 1945 Government statement.

The Ribbon

The Pacific Star ribbon: red edge stripes, a narrow central yellow stripe flanked by wider green, and thin dark blue and light blue stripes. The dark blue, red and light blue symbolize the Navy, Army and Air force. Yellow and green symbolize the forests and beaches.