Possible to set colorscale in 'layout' for heatmap

Is it possible to set colorscale (or something similar) for a heatmap in ‘layout’, something like:_

d3.json(GraphURL, function(err, fig) {
                    fig.layout = {
                      title: 'Title',
                      colorscale='Jet',
                      xaxis: {
                        title: 'Ttile', 
                      },
                      yaxis: {
                        title: 'Title',
                      },
                    };
                    Plotly.newPlot('heatmap', fig.data, fig.layout);
                });

No, colorscale is a trace attribute.