From your 'My Hub' page (please see below)
On the left hand side of your account, you will see the side menu where you can select 'Settings'.
If you click 'Customisation' tab from the 3 options at the top of your page
You will be able to upload your logo within your account and change your colour scheme which all of your clients will see on their side too!
Just remember to hit the 'Update' button to save the changes.