This tutorial shows how to modify the basic colors in Joomla template.
Depending on your design the colored parts can be created using CSS colors or images.
In case your template has plain colors you can change them editing the CSS files from the templates/theme###/css folder of your Joomla installation. The browser developer tool will become handy in this case. Feel free to check the video tutorial on how to use browser tools to edit the template styles.
In case your design has some complex images like illustrations, gradients etc – then your changes should be done in the PSD files. PSD files are located in the template package sources/psd folder. To edit psd files you need Adobe Photoshop software.
Feel free to check the detailed tutorials on how to change colors in Joomla template.