Add in an opacity() color function.

[ajcates]

Often times it is useful to take say @darkblue and set its opacity to about 50% for text shadows. Being able todo this like you use the other color functions would be super handy.

For example the following:

@blue : #00f;
h1 {
    text-color: @blue;
    text-shadow: opacity(darken(@blue, 10%), .5);
}

Would produce:

h1 {
    text-color: #00f;
    text-shadow: rgba(0, 0, 230, .5);
}

[ticaboo]

I think you want

fadeout(@color, 50%);