Add a welcome message dashboard widget and remove any WordPress dashboard widgets with this plugin.
It depends on how much work you are willing to do. The colour is set by CSS code in the php file (which can be edited, but keep in mind that any changes made may be wiped by an update that we may create. We are looking at enabling the user to have a choice of background colours for the next update.
This issue is caused by some HTML syntax errors. Check your site level or network entry and ensure that your HTML code is clean. We are hoping to introduce a filter for the most common syntax errors in our next patch; however, clear and clean text and HTML code is recommended nonetheless.