[Hardly contrails, more like crop spraying! ]
I personally have never seen a brown contrail, but
it looks like we have one here.
http://www.weatherwars.info/
And this is supposed to be normal; if so these engines need a redesign. http://www.weatherwars.info/
Note the brown coloring lasting for about 2-300
meters behind number 2 turbine.
http://www.weatherwars.info/
What a brown contrail! The low sun angle just amplifies the sandy color. http://www.weatherwars.info/