The nodes wire was using 'TH_HEADER' flag to get its color and thus would be in sync with the header. Now make it so it uses its 'own' flag (actually 'TH_SYNTAX_R', the only TH_SYNTAX_* which wasn't yet used by the nodes). Also expose the setting to the user so it can be themified. This fixes T42209 Reviewers: lukastoenne Reviewed By: lukastoenne Maniphest Tasks: T42209 Differential Revision: https://developer.blender.org/D827