Update src/stylesheets/_datacite_colors.scss

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: jrhoads

src/stylesheets/_datacite_colors.scss

@@ -17,4 +17,4 @@ $datacite-lime:               #E2E254 !default;
 
 // Gradient endpoints (for backgrounds, infographics)
 $datacite-gradient-start:     $datacite-primary-light-blue !default;
-$datacite-gradient-end:       #243B53 !default;
+$datacite-gradient-end:       $datacite-primary-dark-blue !default;