Q: How can one have another colour theme as the default colour theme?

A:

(1) You'll need to edit the index.php file.

Please access the index.php file and find the line <!-- Start of Stylesheet Section--> and <!-- End of Stylesheet Section -->. What you'll need to edit are the code in between these two lines. 

For example,if you want to have red colour theme as the default colour theme. Find this line:

<link href="<?php echo $mosConfig_live_site;?>/templates/<?php echo $mainframe->getTemplate(); ?>/css/red.css" rel="alternate stylesheet" type="text/css" title="red"/> 

Delete 'alternate' so it'll be rel="stylesheet", and move this line up, just below <!-- Start of Stylesheet Section--> so that it is the first line of the stylesheet section.

And then, find this line: <link href="<?php echo $mosConfig_live_site;?>/templates/<?php echo $mainframe->getTemplate(); ?>/css/green.css" rel="stylesheet" type="text/css" title="green"/>

Add 'alternate' so it'll be rel="alternate stylesheet".

 (2) You'll then need to edit the css files.

Open your red.css file, Select All and copy the css code in it. Now open the template_css.css file and find the line /*default colour style here, the default one here is green */, delete the lines below it and paste the code in, save file.

And that should be it!