You can buy Gold Roses and Pink lilies from the seed shop in Digitown. Simply walk to the backdoor of the shop, down the stairs next to the normal shopkeeper, and there'll be another dwarf who has an afro down below. Gold Roses cost about 7000g, and Pink Lilies about 21000g each, but are the best for making their respective colours. It takes about 30 Gold Roses to make a single Gold Paint, but only about 8-10 Pink Lilies to make Pink Paint.
Your signature is appended to the bottom of every post you make. If you choose to manually change it, note that it must still conform to the maximum size limit.