Yes. Although, synchronizing it to how you're using Chapel's macros may, or may not, be an issue. As to how, you could either use CSS animations or jQuery to accomplish your goal. Ideally, it would be better to have one source for both animations—background and text flash.
For this example, I'm going to use a CSS transition animation.
Here are the requisite styles: (goes in Story Stylesheet)
transition: background-color 1s ease;
Here is the example using the styles: (see: <<timed>>, <<addclass>>, <<removeclass>>)
<<fadein 1s 2s>>\
<<fadeout 0.5s 3.5s>>\
<<addclass "body" "bgred">>
<<removeclass "body" "bgred">>
<<print either("$AttackA", "$AttackB", "$AttackC")>>
PS: In the future, if you're asking for help using, or integrating, a third-party macro, library, whatever, please supply a link.