Yes. The purple notes have been introduced recently to avoid the confusion between the brown 5TL and the very similar coloured 50TL notes.
Apparently, there have been a number of reports in the past of people handing over 50TL notes and being told that they had only handed over a 5TL note and therefore being short changed.
I think, as has been the case with currency changes in the past, the old notes will be gradually withdrawn over a year and then will cease to be legal tender. You'll still be able to change them at branches of Ziraat Bankasi for a further 10 years after that.
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