The default colour of notes in Microsoft Outlook 2010 is yellow.
Outlook 2010 provides option to change the notes colour using Note Outlook Options. This can be done by clicking on the File menu –> Options link and navigate to Notes and Journal options.
Under Notes options using the Default Colour you can select your desired colour from the available colours. For example if you set the default colour to green then Notes would look as shown below
Demo Video – Change notes colour in Outlook 2010