I have installed spf13-vim plugin and when I set :color molokai
the following orange highlighting occurs;
Does anyone know which setting I need to change to disable the highlighting?
It's not the result of a search, that was my first guess! It doesn't seem confined to any one particular object type either as you can see from the picture.
You need to find out which syntax group causes the highlighting. :syn list
shows all active groups, but it's easier when you install the SyntaxAttr.vim - Show syntax highlighting attributes of character under cursor plugin. When you have the name of the offending syntax group, you can investigate where it comes from; (the last lines of) :scriptnames
may help.
PS: Vim "distributions" like spf-13 and Janus lure you with a quick install and out-of-the-box settings, but you pay the price with increased complexity (you need to understand both Vim's runtime loading scheme and the arbitrary conventions of the distribution) and inflexibility (the distribution may make some things easier, but other things very difficult). Vim is incredibly customizable, using someone else's customization makes no sense.