Qt Creator tips

First, I suggest turning off font anti-aliasing, especially on Windows. You can do it in Tools → Options → Text Editor → Font & Colors or by adding following line to QtCreator.ini in TextEditor section:

FontAntialias=false

Put it in your QtCreator.ini:

[TextEditor]
AddedLine="#e0e0e0;#406040;false;false"
Comment="#40c040;invalid;false;false"
CurrentLine="#c0c0c0;#303030;false;false"
CurrentLineNumber="#808080;#101010;true;false"
DiffFile="#c0c0ff;invalid;false;false"
DiffLocation="#ffffc0;invalid;false;false"
DisabledCode="#a0a0a0;invalid;false;false"
Doxygen.Comment="#40c0a0;invalid;false;false"
Doxygen.Tag="#40c0a0;invalid;true;false"
Keyword="#e0e000;invalid;false;false"
Label="#e00000;invalid;false;false"
LineNumber="#808080;#000000;false;false"
Link="#ffffff;invalid;false;false"
Number="#00e0e0;invalid;false;false"
Operator="#e0e0e0;invalid;false;false"
Parentheses="#c0c0c0;#404040;false;false"
Preprocessor="#0070e0;invalid;false;false"
RemovedLine="#e0e0e0;#604040;false;false"
SearchResult="#c0c0c0;#606000;false;false"
SearchScope="#c0c0c0;#303000;false;false"
Selection="#c0c0c0;#306018;false;false"
String="#00e000;invalid;false;false"
Text="#c0c0c0;#202020;false;false"
Type="#e07000;invalid;false;false"

Put below dark.xml in color schemes directory:

<?xml version="1.0" encoding="UTF-8"?>
<style-scheme version="1.0" name="Dark">
  <style name="AddedLine" foreground="#e0e0e0" background="#406040"/>
  <style name="Comment" foreground="#40c040"/>
  <style name="CurrentLine" foreground="#c0c0c0" background="#303030"/>
  <style name="CurrentLineNumber" foreground="#808080" background="#101010" bold="true"/>
  <style name="DiffFile" foreground="#c0c0ff"/>
  <style name="DiffLocation" foreground="#ffffc0"/>
  <style name="DisabledCode" foreground="#a0a0a0"/>
  <style name="Doxygen.Comment" foreground="#40c0a0"/>
  <style name="Doxygen.Tag" foreground="#40c0a0" bold="true"/>
  <style name="Keyword" foreground="#e0e000"/>
  <style name="Label" foreground="#e00000"/>
  <style name="LineNumber" foreground="#808080" background="#000000"/>
  <style name="Link" foreground="#ffffff"/>
  <style name="Number" foreground="#00e0e0"/>
  <style name="Occurrences" foreground="#e0e0e0" background="#404040"/>
  <style name="Occurrences.Rename" foreground="#e0e0e0" background="#404080"/>
  <style name="Occurrences.Unused" foreground="#a0a0a0" background="#000000"/>
  <style name="Operator" foreground="#e0e0e0"/>
  <style name="Parentheses" foreground="#c0c0c0" background="#404040"/>
  <style name="Preprocessor" foreground="#0070e0"/>
  <style name="RemovedLine" foreground="#e0e0e0" background="#604040"/>
  <style name="SearchResult" foreground="#c0c0c0" background="#606000"/>
  <style name="SearchScope" foreground="#c0c0c0" background="#303000"/>
  <style name="Selection" foreground="#c0c0c0" background="#306018"/>
  <style name="String" foreground="#00e000"/>
  <style name="Text" foreground="#c0c0c0" background="#202020"/>
  <style name="Type" foreground="#e07000"/>
  <style name="VisualWhitespace" foreground="#404040"/>
</style-scheme>

Now in Tools → Options → Text Editor → Font & Colors you can choose my Dark color scheme.

Screenshots from old Qt Creator versions aren't updated, so you can spot tiny differences in colors between them.