This filefish is quite distinctive. It has a flattened body and long tail fin. Typically, it has a pale body with blue spots and scribbly lines, which is where it gets its name. It also has the ability to darken to a camouflage pattern, which is what this one was doing, though the blue lines are still visible. When sporting the camouflage pattern, they lie on the coral and blend in very well indeed.
In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.