Left is Rubys 'Hood' Badge as it existed on a wall of her Pub before I repainted it. Right is the same badge during re-painting. The finished badge can be seen on the 1919 Official Badge page. The bones of every offical British Navy badge whatever the shape, is the Crown, Nameboard and Cableboarder, this is also the standard for Fleet Air Arm Squadron Badges and for Ships of the Royal Australian and Royal Canadian Navies.
The crown originates from a Roman design and should be gold, the ruby, pearl, emerald, and sapphire jewels should be the only other colours, the Nameboard should be gold with black lettering and the Cableboarder should be gold. It is very common to see Badges with artistic license to make them appealing checkout Ebay just type in hms crests.
As with all painting there's an amount of preperation work to be done! Firstly check the badge is clean and free of dust, you can clean the badge briefly with a sponge and hot soapy water then leave to dry!
Once dry paint perferably with a reference to work from!