documentclass{standalone}
usepackage{tikz}
tikzset{
  arrow/.style = { -stealth, red, line width = 2mm,
    postaction = { draw, blue, line width = 1mm, shorten >=1mm }
  }
}
begin{document}
  begin{tikzpicture}
    draw[arrow] (0,0)  --  (+1,+1);
    draw[arrow] (0,0) edge (-1,-1);
  end{tikzpicture}
end{document}

documentclass{standalone}
usepackage{tikz}
tikzset{
  arrow/.style = {-stealth, draw=red, line width = 2mm,
    postaction = { draw=blue, line width = 1mm, shorten >=1mm }
  },
  earrow/.style={
    every edge/.style={arrow}
  }
}
begin{document}
  begin{tikzpicture}
    draw[arrow] (0,0)  --  (+1,+1);
    draw[earrow] (0,0) edge (-1,-1);
  end{tikzpicture}
end{document}

documentclass[border=20pt]{standalone}
usepackage{tikz}
usetikzlibrary{arrows.meta}
tikzset{
  arrow/.style = {
    draw,
    red,
    stealth-stealth,
    line width = 2mm,
    postaction = {
        draw,
        blue,
        line width = 1mm,
        shorten >=1mm,
        shorten <=1mm,
        stealth-stealth
    }
  }
}
begin{document}
  begin{tikzpicture}
    draw[arrow] (-1,-1)  --  (1,1);
    draw[arrow] (1,-1)  -|  (3,1);
    draw[arrow] (4,-1)  .. controls +(right:2cm) and +(down:2cm) .. (6,1);
  end{tikzpicture}
end{document}