bluestars
congratulations and wellcome.now regarding the colour of shoes,am assuming you are female,therefore with the current uniform you will need blue.the new uniform is supposedly being phased in from 13/04 and as you would expect with 13000 cabin crew will take sometime but in answer to your question i think its safe to assume you will probably need the blue ones.
i started flying with ba 20 years ago and i remember being in the same predicament regarding handing in my notice without written confirmation from ba ,they did not do it then and as far as i am aware they still don't .if they offer you the job over the phone i shouldn't worry to much about it but if you really aren't happy just give them a ring and tell them of your concerns
good luck with your training and you never know you might get the new uniform before i do.