In my own apartment, the tiny bathroom has the only walls painted something other than white or gray (teal).
The examples above show how colorful paint, tile, and wallpaper can liven up any style of bathroom. If the collage in Image 1 is a bit much for you, calm but colorful aqua is a good standby (Images 4 and 10).
Images: 1. Lonny 2. Heath Ceramics for Design*Sponge 3. Elle Decor 4. Contented Sparrow 5. Domino via Southern Inspirations 6. Canadian House and Home via Desire to Inspire 7. Elsie Marley 8. Living Etc. 9. via Terramia 10. Country Living