But would Legolas want his choice of colour to be governed by the hares of Mirkwood? Most likely, he would choose it himself. I still believe that, purple being the favourite, his hare would be lavender. Elves do not allow themselves to be governed by foreign forces; they govern themselves and therefore govern the colour of their hares. I found a passage in the Tale of Years that may help determine when Legolas obtained and changed the colour of this hare:
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April
6 A messenger hare from Rivendell reaches Mirkwood bearing the news about the Council; Legolas keeps it and is forced to journey to the council as punishment by Thranduil.
12 Gandalf reaches Hobbiton.
15 Legolas takes his hare in secret and changes the colour of its fur; the colour remains unrecorded in this account.