Generate random colors in Sass. Article - http://pankajparashar.com/posts/random-colors-sass/

random-colors.css

.random-color {
    border-top-color: "LightCoral";
    border-right-color: #a44b58;
    border-bottom-color: rgb(108, 188, 134);
    border-left-color: rgb(24%, 88%, 5%);
    outline-top-color: hsl(88, 69%, 69%);
    outline-right-color: rgba(220, 71, 132, 0.69);
    outline-bottom-color: rgba(79%, 47%, 14%, 0.37);
    outline-left-color: hsla(111, 31%, 38%, 0.86);
}

random-colors.scss

// ----
// Sass (v3.3.9)
// Compass (v1.0.0.alpha.20)
// ----

$named-colors: 'AliceBlue', 'AntiqueWhite', 'Aqua', 'Aquamarine', 'Azure', 'Beige', 'Bisque', 'Black', 'BlanchedAlmond', 'Blue', 'BlueViolet', 'Brown', 'BurlyWood', 'CadetBlue', 'Chartreuse', 'Chocolate', 'Coral', 'CornflowerBlue', 'Cornsilk', 'Crimson', 'Cyan', 'DarkBlue', 'DarkCyan', 'DarkGoldenRod', 'DarkGray', 'DarkGrey', 'DarkGreen', 'DarkKhaki', 'DarkMagenta', 'DarkOliveGreen', 'Darkorange', 'DarkOrchid', 'DarkRed', 'DarkSalmon', 'DarkSeaGreen', 'DarkSlateBlue', 'DarkSlateGray', 'DarkSlateGrey', 'DarkTurquoise', 'DarkViolet', 'DeepPink', 'DeepSkyBlue', 'DimGray', 'DimGrey', 'DodgerBlue', 'FireBrick', 'FloralWhite', 'ForestGreen', 'Fuchsia', 'Gainsboro', 'GhostWhite', 'Gold', 'GoldenRod', 'Gray', 'Grey', 'Green', 'GreenYellow', 'HoneyDew', 'HotPink', 'IndianRed', 'Indigo', 'Ivory', 'Khaki', 'Lavender', 'LavenderBlush', 'LawnGreen', 'LemonChiffon', 'LightBlue', 'LightCoral', 'LightCyan', 'LightGoldenRodYellow', 'LightGray', 'LightGrey', 'LightGreen', 'LightPink', 'LightSalmon', 'LightSeaGreen', 'LightSkyBlue', 'LightSlateGray', 'LightSlateGrey', 'LightSteelBlue', 'LightYellow', 'Lime', 'LimeGreen', 'Linen', 'Magenta', 'Maroon', 'MediumAquaMarine', 'MediumBlue', 'MediumOrchid', 'MediumPurple', 'MediumSeaGreen', 'MediumSlateBlue', 'MediumSpringGreen', 'MediumTurquoise', 'MediumVioletRed', 'MidnightBlue', 'MintCream', 'MistyRose', 'Moccasin', 'NavajoWhite', 'Navy', 'OldLace', 'Olive', 'OliveDrab', 'Orange', 'OrangeRed', 'Orchid', 'PaleGoldenRod', 'PaleGreen', 'PaleTurquoise', 'PaleVioletRed', 'PapayaWhip', 'PeachPuff', 'Peru', 'Pink', 'Plum', 'PowderBlue', 'Purple', 'Red', 'RosyBrown', 'RoyalBlue', 'SaddleBrown', 'Salmon', 'SandyBrown', 'SeaGreen', 'SeaShell', 'Sienna', 'Silver', 'SkyBlue', 'SlateBlue', 'SlateGray', 'SlateGrey', 'Snow', 'SpringGreen', 'SteelBlue', 'Tan', 'Teal', 'Thistle', 'Tomato', 'Turquoise', 'Violet', 'Wheat', 'White', 'WhiteSmoke', 'Yellow', 'YellowGreen';

@function randomizeColor(){
  $color: (
    octal: (
      red: random(256)-1,
      green: random(256)-1,
      blue: random(256)-1
    ),
    percent: (
      red: random(101)-1,
      green: random(101)-1,
      blue: random(101)-1,
      saturation: random(101)-1,
      light: random(101)-1
    ),
    deg: (
      hue: random(361)-1
    ),
    fraction: (
      alpha: random(100)/100
    )
  );
  @return $color;
}

@function color($base, $component) {
  $color: randomizeColor();
  @return map-get(map-get($color, $base), $component);
}

@function getRandomColor($format: NULL) {
  @if $format == "hex" {
    @return rgb(color(octal, red), color(octal, green), color(octal, blue));
  }
  @else if $format == "rgb" { 
    @return unquote("rgb(#{color(octal, red)}, #{color(octal, green)}, #{color(octal, blue)})");
  }
  @else if $format == "%rgb" { 
    @return unquote("rgb(#{color(percent, red)}%, #{color(percent, green)}%, #{color(percent, blue)}%)");
  }
  @else if $format == "rgba" { 
    @return unquote("rgba(#{color(octal, red)}, #{color(octal, green)}, #{color(octal, blue)}, #{color(fraction, alpha)})");
  }
  @else if $format == "%rgba" { 
    @return unquote("rgba(#{color(percent, red)}%, #{color(percent, green)}%, #{color(percent, blue)}%, #{color(fraction, alpha)})");
  }
  @else if $format == "hsl" { 
    @return unquote("hsl(#{color(deg, hue)}, #{color(percent, saturation)}%, #{color(percent, light)}%)");
  }
  @else if $format == "hsla" { 
    @return unquote("hsla(#{color(deg, hue)}, #{color(percent, saturation)}%, #{color(percent, light)}%, #{color(fraction, alpha)})");
  }
  @else { 
    @return nth($named-colors, random(147));
  }
}

.random-color {
  border-top-color: getRandomColor();
  border-right-color: getRandomColor("hex");
  border-bottom-color: getRandomColor("rgb");
  border-left-color: getRandomColor("%rgb");
  outline-top-color: getRandomColor("hsl");
  outline-right-color: getRandomColor("rgba");
  outline-bottom-color: getRandomColor("%rgba");
  outline-left-color: getRandomColor("hsla");
}

@yairEO - You could be passing the result of random color function to another function that works with say, rgba components but not hex, for example.

getRandomColor() should also add the function unquote to process the default output.

@function getRandomColor($format: NULL) {
  // codes before 
  @else { 
    @return unquote(nth($named-colors, random(147)));
  }
}