The following helpsheet will show you how to change the colours on your Channl site from your Dashboard.
Step 1 - from your Channl dashboard click on the 'Manage Yor Site' button as shown below.
Step 2 - click on the Appearance option from the list as shown below.
Step 3 - change the colours for the areas of your Channl site to the ones you want and then click 'Save Changes' to make the changes live.