I configure the powerline theme on OSX like
But it has a strange colour in the ">" character
How can I make the the ">" character colour match with the powerline bar
There's not much you can do about it (except trying a different font).
I had the same "issue" but I don't consider this as something bad. Get use to it but first try a font that will match as much as possible and will reduce the difference between "rectangle" section and "triangle" section.
Check my OMZ shell script where I use bullet-train theme.
Bullet Train theme for OMZ requires Powerline Compatible Fonts
Take a look especially at:
mkdir $TEMP_FONT_DEST cd $TEMP_FONT_DEST git clone https://github.com/powerline/fonts.git . ./install.sh rm -rf $TEMP_FONT_DEST
I will upvote your question because you're new here and to wake up your creativity. Good luck with customising your shell.