Here's how you can change the forum's default pink background to a more manly blue colour...

» Member's CP » Edit Profile » Style » "Discuz Style" (then click "Submit")

And while we're here, if you need to, you can also make all those avatar images of huge dicks and/or scroll-unfriendly signatures disappear too...

» Member's CP » Edit Profile » Signature Configuration » "No signature"
» Member's CP » Edit Profile » Avatar Configuration» "No avatar"