Unlike the US in which the currency is issued only by the US Treasury, currency in Hong Kong is issued by three different banks: Bank of China, Standard Chartered Bank, and HK Shanghai Banking Corp.
So, the currency in Hong Kong can look completely different even if it is for the exact same value! The size of the bills are only slightly different, but the patterns and colors can be completely different.
Check out this photo of three different HK$20 bills.
