Hi Nancy,
No. And yes.
The bad news is that InputBox and MsgBox are built-in functions whose properties are not exposed in the Excel/VBA object model and therefore can't be changed.
The good news is that it is easy to design your own input box and message box functionality by designing a custom UserForm. When you do this you have control of colors and many other properties of the form and the controls on it. If you are not familiar with UserForms, look them up in the VBA helps--they are fairly easy to design.