Change chart colors - d3.js

Question

I have a bar chart/histogram, all working fine.
I need to change the text and lines on the chart is on a black background.I
Also, the bar colors need to be orange.
I have had a look around the web, and seen some references to .attr("style":...); and have tried this without success.
Any pointers gratefully received.
<script>
// set the dimensions of the canvas
var margin = {top: 20, right: 20, bottom: 70, left: 40},
width = 1890 - margin.left - margin.right,
height = 400 - margin.top - margin.bottom;
// set the ranges
var x = d3.scale.ordinal().rangeRoundBands([0, width], .05);
var y = d3.scale.linear().range([height, 0]);
// define the axis
var xAxis = d3.svg.axis()
.scale(x)
.orient("bottom")
var yAxis = d3.svg.axis()
.scale(y)
.orient("left")
.ticks(10);
// add the SVG element
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform",
"translate(" + margin.left + "," + margin.top + ")");
// load the data
d3.json("/assets/js/risk_hist_values.json", function(error, data) {
// the number of columns in this chart
var numCols = data.length;
data.forEach(function(d) {
d.Letter = d.bin_no;
d.Freq = +d.count;
});
// scale the range of the data
x.domain(data.map(function(d) { return d.Letter; }));
y.domain([0, d3.max(data, function(d) { return d.Freq; })]);
var tip = d3.tip()
.attr('class', 'd3-tip')
.offset([-10, 0])
.html(function(d) {
return "<strong>Count:</strong> <span style='color:red'>" + d.count + "</span>";
})
// call the tips
svg.call(tip);
// add axis
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis)
.selectAll("text")
.style("text-anchor", "end")
.attr("dx", "-.8em")
.attr("dy", "-.55em")
.attr("transform", "rotate(-90)" );
svg.append("g")
.attr("class", "y axis")
.call(yAxis)
.append("text")
.attr("transform", "rotate(-90)")
.attr("y", 5)
.attr("dy", ".71em")
.style("text-anchor", "end")
.text("Count");
// Add bar chart
svg.selectAll("bar")
.data(data)
.enter().append("rect")
.attr("class", "bar")
.attr("x", function(d) { return x(d.Letter); })
.attr("width", x.rangeBand())
.attr("y", function(d) { return y(d.Freq); })
.on('mouseover', tip.show)
.on('mouseout', tip.hide)
.on('click', drill)
.attr("id", function(d, i){ return 'b_'+i+''; })
.attr("height", function(d) { return height - y(d.Freq); });
});
function drill(){
alert( 'drilling' );
}
</script>