Spatial join by categories in QGIS

I am using QGIS 2.4.0 and I have a vector layer which contains a remoteness indicator which is broken up into 5 categories. I would like to turn this into a layer that has these 5 categories collapsed into 2. On the included map I would like to join the green areas together into one group and the yellow and red areas into another group. Any advice would be much appreciated

In the attribute table included I would like to join together the categories in the RA_Name11 field.

My apologies if this is a simple task, I just haven't got a good starting point for identifying keywords.