I personally use Tomcat for hosting my web application and employ apache http server on the top from it using mod proxy for load balancing.

When my application throws a 404 or 500 error, I wish to serve the mistake pages through apache http server instead of tomcat server. The reason being I'm serving all my static content through apache and that we do not want it included in war. It is possible to way I'm able to do this? I could not find anything searching it.

Specify the "ErrorDocument" directive within the virtualhost portion of your apache config:

ErrorDocument 404 /path/to/my404page.html
ErrorDocument 500 /path/to/my500page.html

Furthermore, since you are using mod proxy, you might you may decide to enable ProxyErrorOverride to allow apache generate custom error documents for proxied content.

Also take a look at the documentation