When using RadSplitter for ASP.NET AJAX
the borders can be removed very easy - the RadSplitter'
s BorderSize and PanesBorderSize
properties are designed to control the borders' appearance. To remove all the RadSplitter's borders you should set BorderSize="0".
In the same manner, to remove the RadPanes' borders you should set PanesBorderSize="0".
As to changing the color, all you need to do is to use the IEDevToolBar or Firebug tools, find the particular CSS classes and set the desired color there.
the Telerik team