there's a difference in features , there are more features in denim than cyan.
DENIM FEATURES---------------
Cortana ? The most personal digital assistant on the market will now be available in the UK and China as a Beta. India, Canada and Australia will have access to Cortana as a public Alpha. For US residents, Cortana now includes an improved natural language, car kit integration via Bluetooth for contacts, snooze reminders and calendar improvements.
Live folders ? If you prefer to keep your apps or games organised, you can now put them into folders. Simply press, hold and drag an app over another to create a new folder on the Start screen. Each folder can be renamed by tapping on the text field above the open folder.
Apps Corner ? Create a customised Start screen, where only specific apps or games are accessible. This could be particularly useful in the workplace if you?re issuing Windows Phones to employees.
SMS merge and forwarding ? Select individual text messages to either delete them out of a messaging thread, or to copy and past them into a new message in order to forward them.
Snooze Times ? It?s now possible to customise the snooze time within the Alarm app.
Consumer VPN ? Maintain privacy and security when using data while connected to public Wi-Fi hotspots or even with your home Wi-Fi.
Mobile Web Site improvements in IE ? Connect and browse even faster with improved downloading speeds on mobile websites.
Store Live Tile (US only) ? The Store Live Tile displays featured apps and games that are the most popular in the Store, or most relevant for you.