This is very easy trick to change the color of Selected Text in blogger.to change thecolor of selected just login in to blogger and go to Template Editing
Find </head> tag and just after that put the below code
<style type="text/css">
::selection {background:#cc0000;color:#ffffff;}
::-moz-selection{background:#cc0000;color:#ffffff;}
code::selection {background: #333333;color:#ffffff;}
code::-moz-selection {background: #333333;color:#ffffff;}
pre::selection {background: #44ceff;color:#ffffff;}
pre::-moz-selection {background: #44ceff;color:#ffffff;}
</style>
Note-You can change the your color according to your wish ..use this HTML Color code calculator to get color code
