1. Is it possible to copy the current ledger from one PC to another? My colleague is about to open a new Bitcoin Core wallet and I want to know if I can copy my ledger to his PC so he doesn't have to download the whole thing.
Definitely. Just a note though, it is not completely decentralised, given that it was verified by someone else (you) and not your colleague him/herself. There are several information which can identify you so you should be able to just transfer the blocks and chainstate folder to your colleague. Do not transfer the wallet.dat file or database.
2. How do I create a new wallet within the Bitcoin Core client? I am transferring the existing wallet to my colleague but I want to open a new wallet in my client to receive Bitcoin from him.
Thanks
If you are trying to generate a new address, go to File>Receiving addresses and click on New. A new address will be shown to you.
If you want to create a new wallet, remove the wallet.dat from that directory and a new wallet.dat will be generated when you run the Core client next time.