Pushing up an old post of mine. Options to change the page colors on client side have been possible for years. One only have to know how. Some of them are easy, some requires little effort.

Stylish

Various dark skins for ipernity available here: userstyles.org/styles/browse?search_terms=ipernity&type=false

You need to install Stylish extension to use it: userstyles.org/help/stylish

My version of these provides also an option to get rid of the z.gif: www.ipernity.com/blog/serola/4716848

And if you know how, you can make a skin of your own, even a pink one if you like. But I warn you that it is extremely complicated. Most of the current dark skins are based on the hard ground work done by Spotomy: www.ipernity.com/blog/spo/4655884

Dark Reader

Available here: darkreader.org

I have not yet tested this, and therefore I really can't guarantee how reliable it is.

I am using Dark Reader now on Chrome, and already default settings, are treat for my eyes! Just the right contrast =)

Please notice you can set web site specific exceptions on Dark Reader.

Moreover, Isabel (Xata) has reported that Dark Reader works even on iPhone and iPad (Safari).

Although, it is advised to disable all other similar tools on Dark Reader pages, it still may work for example together with Stylish. So, if you wish to use Stylish instead on some web site, then add that web site as and exception on Dark Reader, and use the Stylish style instead.

Tampermonkey

Get Tampermonkey: www.tampermonkey.net

See the comment by Marta.