How To: Change Block Text Color
There can be multiple reasons why your styles are not applied to the page elements:


CSS aggregation is enabled. Disable aggregation and see if your custom CSS works. If it doesn't, you probably forgot to include the file in your theme - move to the next option.
CSS stylesheet is not added to the theme via THEMENAME.info file or other methods. Placement of the CSS file in your theme's css folder does not make it load while Drupal pages are loading. 
wrong selector used
styles are overridden by a selector with higher specificity  ...etc.


To add CSS stylesheet to the Drupal theme, add the following to the current theme's .info file and clear cache:

stylesheets[all][] = css/local.css


You can also add CSS files to your theme via drupal_add_css function that you can use in hook_preprocess_page().

Hope this helps.