Black title changes colour when exporting MXF ??? Been asked by client to export in MXF format. Never done that before (worked within PP with MXF, just never exported to that).

At the end of the ad I've made a very simple after effects title/call to action. Simple black text over the final shot.

Everything fine when I exported h264 mp4. But when exporting MXF, the black title went green.

Any ideas why? Help appreciated.
Might be an issue with the smart rendering option available for MXF in Premiere/AME.
Try disabling that.

http://blogs.adobe.com/kevinmonahan/2012/10/11/smart-rendering-in-premiere-pro-cs6-6-0-1-and-later/

If that doesn't work. Render an intermediate and re-import and encode that to MXF.
Though keep in mind that MXF is just a container, you have different codecs available.
Make sure you choose the one suitable for your source footage and what your client requested.