Effective design is more important that exciting design
If this is a system you want users to feel comfortable learning and using frequently, your primary goal should be to provide an interface (including a set of colors) that allows users to manipulate their cloud files as quickly and effectively as possible.
Once that goal has been accomplished, you can decide on a secondary goal of how to provide details (colors, animations, etc) which can enhance marketing appeal for the product.
If you are choosing bright colors and high contrast just to draw attention, you may violate the primary goals because your interface becomes visually distracting to users who are just trying to do simple file manipulation but now have to read glaring white-on-bright-blue text or icons.
You can still use color effectively to draw attention while fulfilling a purpose.
- In your screenshot, the icons are bright blue which creates a lot of visual distraction because there are a lot of files. The blue doesn't actually fulfill any purpose other than to draw attention.
- Instead, you might use blue to show hover-over files, or files being dragged, or page titles, etc. In each of these cases, you are using bright colors in a functional rather than a purely decorative (and potentially distracting) way.
A canonical example of effective but striking/enticing interface design is the original iPod, which did not need bright colors to entice users but rather provided elementary shapes (square, circle) and functional minimalism to draw appeal while retaining sharp focus on usability.