Curly Ponytail Human Hair Extensions #4 Chestnut Brown

Hi, really love the hair quality - Although haven’t washed it yet. You do no seem to have number 5 and that’s my colour. I ordered a 4 which is slightly darker - I tried a different colour this time, haven’t picked it up from Aust post yet. However my question to you is - can I colour it . or tried to?? What would be the best thing to do? I am just playing with the colours you have on line but a number 5, would be ideal. Cheers