Javascript function to convert color names to hex codes

No, but using the list here you could create one. Something like this:

function colourNameToHex(colour)
{
    var colours = {"aliceblue":"#f0f8ff","antiquewhite":"#faebd7","aqua":"#00ffff","aquamarine":"#7fffd4","azure":"#f0ffff",
    "beige":"#f5f5dc","bisque":"#ffe4c4","black":"#000000","blanchedalmond":"#ffebcd","blue":"#0000ff","blueviolet":"#8a2be2","brown":"#a52a2a","burlywood":"#deb887",
    "cadetblue":"#5f9ea0","chartreuse":"#7fff00","chocolate":"#d2691e","coral":"#ff7f50","cornflowerblue":"#6495ed","cornsilk":"#fff8dc","crimson":"#dc143c","cyan":"#00ffff",
    "darkblue":"#00008b","darkcyan":"#008b8b","darkgoldenrod":"#b8860b","darkgray":"#a9a9a9","darkgreen":"#006400","darkkhaki":"#bdb76b","darkmagenta":"#8b008b","darkolivegreen":"#556b2f",
    "darkorange":"#ff8c00","darkorchid":"#9932cc","darkred":"#8b0000","darksalmon":"#e9967a","darkseagreen":"#8fbc8f","darkslateblue":"#483d8b","darkslategray":"#2f4f4f","darkturquoise":"#00ced1",
    "darkviolet":"#9400d3","deeppink":"#ff1493","deepskyblue":"#00bfff","dimgray":"#696969","dodgerblue":"#1e90ff",
    "firebrick":"#b22222","floralwhite":"#fffaf0","forestgreen":"#228b22","fuchsia":"#ff00ff",
    "gainsboro":"#dcdcdc","ghostwhite":"#f8f8ff","gold":"#ffd700","goldenrod":"#daa520","gray":"#808080","green":"#008000","greenyellow":"#adff2f",
    "honeydew":"#f0fff0","hotpink":"#ff69b4",
    "indianred ":"#cd5c5c","indigo":"#4b0082","ivory":"#fffff0","khaki":"#f0e68c",
    "lavender":"#e6e6fa","lavenderblush":"#fff0f5","lawngreen":"#7cfc00","lemonchiffon":"#fffacd","lightblue":"#add8e6","lightcoral":"#f08080","lightcyan":"#e0ffff","lightgoldenrodyellow":"#fafad2",
    "lightgrey":"#d3d3d3","lightgreen":"#90ee90","lightpink":"#ffb6c1","lightsalmon":"#ffa07a","lightseagreen":"#20b2aa","lightskyblue":"#87cefa","lightslategray":"#778899","lightsteelblue":"#b0c4de",
    "lightyellow":"#ffffe0","lime":"#00ff00","limegreen":"#32cd32","linen":"#faf0e6",
    "magenta":"#ff00ff","maroon":"#800000","mediumaquamarine":"#66cdaa","mediumblue":"#0000cd","mediumorchid":"#ba55d3","mediumpurple":"#9370d8","mediumseagreen":"#3cb371","mediumslateblue":"#7b68ee",
    "mediumspringgreen":"#00fa9a","mediumturquoise":"#48d1cc","mediumvioletred":"#c71585","midnightblue":"#191970","mintcream":"#f5fffa","mistyrose":"#ffe4e1","moccasin":"#ffe4b5",
    "navajowhite":"#ffdead","navy":"#000080",
    "oldlace":"#fdf5e6","olive":"#808000","olivedrab":"#6b8e23","orange":"#ffa500","orangered":"#ff4500","orchid":"#da70d6",
    "palegoldenrod":"#eee8aa","palegreen":"#98fb98","paleturquoise":"#afeeee","palevioletred":"#d87093","papayawhip":"#ffefd5","peachpuff":"#ffdab9","peru":"#cd853f","pink":"#ffc0cb","plum":"#dda0dd","powderblue":"#b0e0e6","purple":"#800080",
    "rebeccapurple":"#663399","red":"#ff0000","rosybrown":"#bc8f8f","royalblue":"#4169e1",
    "saddlebrown":"#8b4513","salmon":"#fa8072","sandybrown":"#f4a460","seagreen":"#2e8b57","seashell":"#fff5ee","sienna":"#a0522d","silver":"#c0c0c0","skyblue":"#87ceeb","slateblue":"#6a5acd","slategray":"#708090","snow":"#fffafa","springgreen":"#00ff7f","steelblue":"#4682b4",
    "tan":"#d2b48c","teal":"#008080","thistle":"#d8bfd8","tomato":"#ff6347","turquoise":"#40e0d0",
    "violet":"#ee82ee",
    "wheat":"#f5deb3","white":"#ffffff","whitesmoke":"#f5f5f5",
    "yellow":"#ffff00","yellowgreen":"#9acd32"};

    if (typeof colours[colour.toLowerCase()] != 'undefined')
        return colours[colour.toLowerCase()];

    return false;
}

This will give it to you in RGB - you should be able to do the hex conversion pretty easily.

d = document.createElement("div");
d.style.color = "white";
document.body.appendChild(d)
//Color in RGB 
window.getComputedStyle(d).color

Get Computed style is not supported on all browsers.

@dlauzon suggested I convert my comment into an answer. Thanks for suggesting! Here it is :)

function standardize_color(str){
    var ctx = document.createElement('canvas').getContext('2d');
    ctx.fillStyle = str;
    return ctx.fillStyle;
}

function standardize_color(str){
    var ctx = document.createElement("canvas").getContext("2d");
    ctx.fillStyle = str;
    return ctx.fillStyle;
}

document.getElementById("myspan1").innerHTML = standardize_color("red");
document.getElementById("myspan2").innerHTML = standardize_color("PeachPuff");
document.getElementById("myspan3").innerHTML = standardize_color("PaleGoldenRod"); 
document.getElementById("myspan4").innerHTML = standardize_color("RGB(123,234,142)"); 
document.getElementById("myspan5").innerHTML = standardize_color("HSL(284,6%,49%)");

span { font-weight:800; }

The color named "Red" has a code of: <span id="myspan1">(requires js)</span>.<br>
 ...and color "PeachPuff"'s code is: <span id="myspan2">(requires js)</span>.<br>
 ...and "PaleGoldenRod" is: <span id="myspan3">(requires js)</span>.<br><br>
 
It works with "RGB(123,234,142)" too: <span id="myspan4">(needs js)</span>  
and therefore with: "HSL(284,6%,49%)", which is: <span id="myspan5">(requires js)
</span>.  Handy!