The Mayor of Abilene Norm Archibald held a press conference to bring attention to the blue lights that are shining in residential windows around Abilene. Mayor Archibald went on to ask Abilene residents to join in and honor fallen heroes and/or first responders by lighting a "Blue Hero Light" in windows this Christmas season. Also at the press conference with the mayor was Annemarie Holder, the widow of Abilene motorcycle police officer Rodney Holder, who died in a traffic accident in 2010.

Most of the neighbors around the Holders neighborhood have placed blue lights in their windows. Now Mayor Archibald is urging retailers to stock up on blue lights so Abilene residents can easily find them. Hardin-Simmons University was so moved by the gesture that they added a "Blue Hero Tree" to the campus lighting scheme.

Annemarie Holder says she and Kyler, the Holders 14-year-old son, drove by the HSU campus to view the tree after someone mentioned it to her. “I just wanted to let you know how much we appreciate the Blue Hero Tree at the entrance of your campus. We were so touched! Thank you so much, for your obvious support of our First Responders. It means so much to our family to see that,” Holder stated in an email to the president’s office. “Please let all of those responsible for this display know how much we appreciate it,” said Holder.

source: HSU press release

You can view the Hero Tree at the entrance to the HSU campus located at Ambler and Hickory. Other places in Abilene with blue lights on display are the Abilene Police Department and the Holders own neighborhood.
This video shows an Elvis fan that's been using blue lights for decades.