After installing the latest (13 Jan 2016) update all dog collars changed to white and it is no longer possible to dye them different colours.
MCPE-12414
Dog collars no longer dye
Resolved
Duplicate
0
Thank you for your report! This issue was, however, reported at an earlier time as MCPE-12091. Feel free to add any information you find relevant in the comment section there.
If you did not do so this time, please perform a search to see if your bug has already been submitted prior to creating new tickets in the future.