User blog comment:Jrhrjo/A Brief Introduction/@comment-43593768-20190831070544/@comment-36706316-20190831074340

The colored aura means they are a special edition.

Green: H2H fighters which have one or more legendary abilities ( high damage )

Purple: Legendary fighters which have one or more legendary abilities ( high damage )

Red: Limited edition fighters ( higher health / damage than their normal version )

White: Limited edition fighters ( higher health / damage than their normal version )