#columns {
    background: -webkit-linear-gradient(left,rgba(0,0) 50%,blue 50%);
    /*... appropriate css for other browser engines*/
}

updated jsFiddle
使用所有浏览器支持渐变更新

– 编辑 –

因为意图实际上是改变文本颜色而不是第三和第四列的背景一些额外的想法.

目前,似乎无法将样式应用于容器内的单个列.更改特定列中文本颜色的一种可能解决方法是将每个单词放在跨度中.然后使用JavaScript迭代单词并确定新列的开始位置.为第三列中的第一个元素分配一个新类,可以使用不同的文本颜色设置此样式和以下兄弟.

由于容器是响应式布局的一部分,并且可能会更改大小,因此必须在resize事件上重新运行该脚本以考虑更改列宽.

代码示例的目的是概述如何实现这样的解决方案,并且应该在实际应用程序中进行改进(例如,每次运行styleCols时都会重新创建跨度,大量的控制台输出……).

JavaScript的

function styleCols() {
    // get #columns
    var columns = document.getElementById('columns');
    // split the text into words
    var words = columns.innerText.split(' ');
    // remove the text from #columns
    columns.innerText = '';

    // readd the text to #columns with one span per word
    var spans = []
    for (var i=0;i<words.length;i++) {
        var span = document.createElement('span');
        span.innerText = words[i] + ' ';
        spans.push(span);
        columns.appendChild(span);
    }

    // offset of the prevIoUs word
    var prev = null;
    // offset of the column
    var colStart = null;
    // number of the column
    var colCount = 0;
    // first element with a specific offset
    var firsts = [];
    // loop through the spans
    for (var i=0;i<spans.length;i++) {
        var first = false;
        var oL = spans[i].offsetLeft;
        console.info(spans[i].innerText,oL);
        // test if this is the first span with this offset
        if (firsts[oL] === undefined) {
            console.info('-- first');
            // add span to firsts
            firsts[oL] = spans[i];
            first = true;
        }
        // if the offset is smaller or equal to the prevIoUs offset this
        // is a new line
        // if the offset is also greater than the column offset we are in
        // (the second row of) a new column
        if ((prev === null || oL <= prev) && (colStart === null || oL > colStart)) {
            console.info('-- col++',colCount + 1);
            // update the column offset
            colStart = oL;
            // raise the column count
            colCount++;
        }
        // if we have reached the third column
        if (colCount == 3) {
            // add our new class to the first span with the column offset
            // (this is the first span in the current column
            firsts[oL].classList.add('first-in-col3');
            return;
        }
        // update prev to reflect the current offset
        prev = oL;
    }
}
styleCols();
addEventListener('resize',styleCols,false);

CSS

.first-in-col3,.first-in-col3~span {
    color: red;
}

jsFiddle