How to change the text color in Highcharts

check this example, i was able to change labels colours on your jsfiddle. here's whole options parameter:

Highcharts.setOptions({
    chart: {
        style: {
            fontFamily: 'monospace',
            color: "#f00"
        }

    },
    title: {
      style: {
         color: '#F00',
         font: 'bold 16px "Trebuchet MS", Verdana, sans-serif'
      }
   },
    xAxis: {
      gridLineWidth: 1,
      lineColor: '#000',
      tickColor: '#000',
      labels: {
         style: {
            color: '#F00',
            font: '11px Trebuchet MS, Verdana, sans-serif'
         }
      },
      title: {
         style: {
            color: '#333',
            fontWeight: 'bold',
            fontSize: '12px',
            fontFamily: 'Trebuchet MS, Verdana, sans-serif'

         }            
      }
   },
   yAxis: {
      minorTickInterval: 'auto',
      lineColor: '#000',
      lineWidth: 1,
      tickWidth: 1,
      tickColor: '#000',
      labels: {
         style: {
            color: '#F00',
            font: '11px Trebuchet MS, Verdana, sans-serif'
         }
      },
      title: {
         style: {
            color: '#333',
            fontWeight: 'bold',
            fontSize: '12px',
            fontFamily: 'Trebuchet MS, Verdana, sans-serif'
         }            
      }
   },
});

almost every option in high charts can have style applied to it, like I have done to the y-axis in this example:

http://jsfiddle.net/h3azu/

I would also recommend going to this page,

http://www.highcharts.com/demo/combo-dual-axes

and clicking "view options" to get an idea of other ways the 'style' option can be used to color text.