In kibana, I have created a dashboard for aws logins, but for failed login attempts I want legend to be red. How can i customized the legend colors.
You can't, yet. This feature will be coming very soon.
You can do this in Kibana 4.3 in advanced settings:
However, the real fix is coming soon (currently targeted to 4.4) via a UI:
There is a PR already available if someone is interested in checking it out: