Wrong order of CSS files

In template.php you have the following code:

drupal_add_css(
  $touchpro_path . '/styling/css/style.css', array(
    'preprocess' => variable_get('preprocess_css', '') == 1 ? TRUE : FALSE,
    'group' => CSS_THEME,
    'media' => 'screen',
    'every_page' => TRUE,
    'weight' => (CSS_THEME-2)
  )
);

The weight makes this file appear after my own css files in a sub theme based on touchpro. Effectively this means that my overrides do not work unless I make them stronger than the defaults in touchpro.

The default weight is 0. CSS_THEME is a constant meant for the group setting, not for the weight setting, so I guess you meant this (also "correcting" the strange preprocess setting which you can set safely to true, regardless the actual setting of the variable):

drupal_add_css(
  $touchpro_path . '/styling/css/style.css', array(
    'preprocess' => TRUE,
    'group' => CSS_THEME,
    'media' => 'screen',
    'every_page' => TRUE,
    'weight' => -2,
  )
);

Which happens to makes my CSS overrides work as expected.

The same holds for the adding of color.css.