As Roland mentioned in his brief description, he worked on multiple UI elements to improve User Experience. He built a new set of icons which feature an outlined style rather than a filled one. In this way, he managed to make the content cleaner and lighter.
Regarding colors, Roland used bright tones, such as Green, Blue, Orange and Red to emphasize particular elements. He had a particular attention for the icons, transforming the current skeuomorphism-style set to a flat one. In this way, there is more consistency on the platform, also given by the grey-only set of icons in the left navigation bar.