[Plugin: Contact Form 7] Validation Error Background Color

The theme I am using is dark, so the default text color is white. When validation errors occur they don’t show, since the default validation block color is also white. I’ve tried to adjust the css for Contact Form (added background-color: #999 to div.wpcf7-validation-errors and span.wpcf7-not-valid-tip) and the theme (added background color to the child style sheet; .wpcf7 span.wpcf7-not-valid-tip and .wpcf7-not-valid-tip) without success. Found a similar question in support:

http://ww.wp.xz.cn/support/topic/plugin-contact-form-7-yellow-error-on-form-validation-error?replies=4

However, that solution did not work. What am I missing?

PLEASE HELP! Thanks in advance.

http://ww.wp.xz.cn/extend/plugins/contact-form-7/