Using JavaScript, you can set the universal menu color scheme.

var a2a_config = a2a_config || {};
a2a_config.color_bg = "FFFFFF";
a2a_config.color_main = "D7E5ED";
a2a_config.color_border = "AECADB";
a2a_config.color_link_text = "333333";
a2a_config.color_link_text_hover = "333333";

In Drupal, add the following JavaScript code to your "Additional JavaScript" box in Configuration > Web services > AddToAny > Additional Options.

In WordPress, add the following JavaScript code to your "Additional JavaScript" box in Settings > AddToAny.

a2a_config.color_bg = "FFFFFF";
a2a_config.color_main = "D7E5ED";
a2a_config.color_border = "AECADB";
a2a_config.color_link_text = "333333";
a2a_config.color_link_text_hover = "333333";

Tip: Using CSS, you can override any style of the AddToAny menu. For instance, you can have square corners instead of rounded corners.