To shade, I use adjustment layers. When I click on the half white/half black circle at the bottom of the layers, a menu comes up. For this entry, I have chosen Levels to make things lighter and Exposure to darken them. To make it easier to see what I'm changing, I use Ctrl I (Inverse) to change the white layer to black. I then use a white brush to reveal the shading changes.
step 4 of 5
I used the same process to change the tentacle to green. After I changed one, I used Image>Adjustments>Match Color to change all the rest of them.
step 5 of 5
I took the letters off of the boat, rearranged them and renamed the boat.