To update the button colour on your email templates, navigate to Tools>Notifications>Email Templates and choose the relevant template that you would like to change the button colour of. 

• Select the Source button: 

• If you then search for 'background-color:', you will be able to replace the Hex code to the appropriate colour that you would like. 

• You will also need to search for 'fillcolor=', and replace this with the same Hex code for the desired colour to take affect.