CSS Gradients - Less Mixins

I'd do this like so:

.css-gradient(darken(#20416A,10%),darken(#3D69A5,10%))

Of course you could also do:

.css-gradient(@from: #20416A, @to: #3D69A5) {
    background-color: @to;
    background-image: -webkit-gradient(linear, left top, left bottom, from(@from),  to(@to));
    background-image: -webkit-linear-gradient(top, @from, @to);
    background-image: -moz-linear-gradient(top, @from, @to);
    background-image: -o-linear-gradient(top, @from, @to);
    background-image: -ms-linear-gradient(top, @from, @to);
    background-image: linear-gradient(top, @from, @to);
}
.css-gradient(darken,@amount: 10%, @from: #20416A, @to: #3D69A5){
    .css-gradient(darken(@from,@amount),darken(@to,@amount));
}

And then just call it:

.css-gradient(darken,10%);

or:

.css-gradient(#20416A, #3D69A5);

or:

.css-gradient(darken,5%,#00ff00,#ff0000);