This is a spinoff of Obsidian colour scheme for Oracle SQL Developer. It is based on Obsidian Eclipse colour scheme by Morinar.
Unfortunately Oracle doesn't make it easy to import a new colour scheme into SQL Developer, thus a little bit of hacking is required.
Close SQL Developer. This is important. If you modify the scheme file while SQL Developer is open, your changes won't be saved.
dtcache.xmlin the SQL Developer's settings directory. On my system it is located in directory
<schemeMap>tag inside dtcache.xml file. Insert the content of
<schemeMap>alongside the other colour schemes. Be careful not to break the XML.
Launch SQL Developer. Navigate to menu Tools->Preferences, then select item Code Editor -> PL/SQL Syntax Colours in the left pane.
Select "OzBsidian" in the "Scheme" drop down list on the top.
The colours are mostly match Obsidian scheme, although not exactly. For instance, the background is a bit darker. Hence the name is OzBsidian to differentiate it from the original scheme.
You can download the colour scheme with the installation instruction from my GitHub account.