title: Creating a graph with edges of different colours in Mathematica
body: <p>I want to create a graph (Graph Theory) where certain edges have a different colour to other edges, which would be used to highlight a path in the graph from one vertex to another. </p>
  
  <p>Here are some examples which have different coloured edges <a href="http://demonstrations.wolfram.com/AGraphTheoryInterpretationOfTheSumOfTheFirstNIntegers/" rel="nofollow noreferrer">http://demonstrations.wolfram.com/AGraphTheoryInterpretationOfTheSumOfTheFirstNIntegers/</a> and <a href="http://demonstrations.wolfram.com/Ramsey336/" rel="nofollow noreferrer">http://demonstrations.wolfram.com/Ramsey336/</a>. I looked at source code for these but those solutions seem complicated. I need a simple example to work from. I reckon I need to use the EdgeRenderingFunction as one of the options for <code>GraphPlot</code>. </p>
  
  <p>Additionally under <a href="http://reference.wolfram.com/mathematica/ref/EdgeRenderingFunction.html" rel="nofollow noreferrer">EdgeRenderingFunction</a> documentation in "More
  Information" part it says:  </p>
  
  <p><img src="https://i.stack.imgur.com/YJdqw.png" alt="Mathematica graphics"></p>
  
  <p>This looks useful but unfortunately there is no coded examples to try.</p>
  
  <p>Taking that very literally I tried things like </p>
  
  <blockquote>
    <p>GraphPlot[{1 -> 2, 2 -> 3, 3 -> 4, 4
    -> 1, 2 -> 4, 4 -> 5, 4 -> 6},   VertexLabeling -> True,<br>
    EdgeRenderingFunction -> g[{1, 2}, {1,
    2}, Red]]</p>
  </blockquote>
  
  <p>But that wouldn't work. It will take something more clever than that.</p>