title: gnuplot dashed lines are not plotted in color
body: <p>I've been searching for quite some time how to plot dashed lines in gnuplot 5.2, and I've tried some code which was supposed to plot dashed lines, but to no avail. Can someone please help me understand what is wrong in my code that does not allow plotting dashed lines?</p>
  
  <pre><code>reset session
  set term pngcairo dashed
  set output 'dashcolor_1.png'
  set label 1 "set style line 1 lt 2 lc rgb \"red\" lw 3" at -0.4, -0.25, 0 left norotate back textcolor rgb "red"  nopoint offset character 0, 0, 0
  set label 2 "set style line 2 lt 2 lc rgb \"orange\" lw 2" at -0.4, -0.35, 0 left norotate back textcolor rgb "orange"  nopoint offset character 0, 0, 0
  set label 3 "set style line 3 lt 2 lc rgb \"yellow\" lw 3" at -0.4, -0.45, 0 left norotate back textcolor rgb "yellow"  nopoint offset character 0, 0, 0
  set label 4 "set style line 4 lt 2 lc rgb \"green\" lw 2" at -0.4, -0.55, 0 left norotate back textcolor rgb "green"  nopoint offset character 0, 0, 0
  set label 5 "plot ... lt 1 lc 3 lw 3" at -0.4, -0.65, 0 left norotate back textcolor lt 3 nopoint offset character 0, 0, 0
  set label 6 "plot ... lt 3 lc 3 lw 2" at -0.4, -0.75, 0 left norotate back textcolor lt 3 nopoint offset character 0, 0, 0
  set label 7 "plot ... lt 5 lc 3 lw 3" at -0.4, -0.85, 0 left norotate back textcolor lt 3 nopoint offset character 0, 0, 0
  set style line 1  linetype 2 linecolor rgb "red"  linewidth 3.000 pointtype 1 pointsize default
  set style line 2  linetype 2 linecolor rgb "orange"  linewidth 2.000 pointtype 2 pointsize default
  set style line 3  linetype 2 linecolor rgb "yellow"  linewidth 3.000 pointtype 3 pointsize default
  set style line 4  linetype 2 linecolor rgb "green"  linewidth 2.000 pointtype 4 pointsize default
  set noxtics
  set noytics
  set title "Independent colors and dot/dash styles" 
  set xlabel "You will only see dashed lines if your current terminal setting permits it" 
  set xrange [ -0.500000 : 3.50000 ] noreverse nowriteback
  set yrange [ -1.00000 : 1.40000 ] noreverse nowriteback
  set bmargin  7
  unset colorbox
  plot cos(x)     ls 1 title 'ls 1',        cos(x-.2)  ls 2 title 'ls 2',     cos(x-.4)  ls 3 title 'ls 3',     cos(x-.6)  ls 4 title 'ls 4',      cos(x-.8)  lt 1 lc 3 title 'lt 1 lc 3',       cos(x-1.)  lt 3 lc 3 title 'lt 3 lc 3',       cos(x-1.2) lt 5 lc 3 title 'lt 5 lc 3'
  </code></pre>
  
  <p>The code above plots the picture below, but the curves are supposed to be dashed.</p>
  
  <p><a href="https://i.stack.imgur.com/iwEdw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iwEdw.png" alt="enter image description here"></a></p>