Yes, it is possible. For the rain display change AWNgraphs/awngraphs.js
name: wxlegend.rain.rain,
type: 'area',
yAxis: 1,
tooltip: {valueSuffix: ' '+wxuom.rain.units}
to
name: wxlegend.rain.rain,
type: 'area',
color: '#4040FF',
yAxis: 1,
tooltip: {valueSuffix: ' '+wxuom.rain.units}
and change the #4040FF to your desired color.