GIMP, Krita, Darktable, and Inkscape are not made specifically for elementary OS or created with the HIG of elementary OS in mind, but they will get the job done and are available in AppCenter.
elementary OS has it's own photo manager called Photos which also allows for very basic picture manipulation tasks.
GIMP with Separate+
GIMP is a well known image manipulation program and a popular alternative to Photoshop. Although it doesn't have built-in CMYK support, the Separate+ plugin can allow you to convert from RGB to CMYK.
To install GIMP, head to AppCenter. A newer version can also be installed from Flathub.
This is not necessarily a complete solution for CMYK,...
I use Krita. It's a digital painting and illustration application. Krita offers CMYK support, HDR painting, perspective grids, dockers, filters, painting assistants, and many other features.
To install Krita, head to AppCenter. A newer version can also be installed from Flathub.
You can set a different style scheme in org.pantheon.scratch.settings.style-scheme
See this link for how to edit a setting in dconf https://elementaryos.stackexchange.com/a/176/37
Schemes are located in /usr/share/gtksourceview-3.0/styles
and the preinstalled schemes are
It includes both using System Settings > Color and the settings built into your monitor. Go to
System Settings > Color: Click your monitor and then click "View Details" it should ask you to install something. Change the profile then click view details and look at the preview tabs. keep doing this until you find the right one for you
After to get an added ...
Daniel Fore added some code in the stylesheet a few hours ago to fix this. (thanks by the way ;)
You can add these 2 lines by yourself in your gtk-widgets.css or wait for an system update.
The file is in your system folder... /usr/share/themes/elementary/gtk-3.0/
And the changes you can find here...