Create a 2D colour map using hourly solar radiation data and plotting radiation vs day of year

Hi I am calculating the hourly solar radiation as a end result in a model and i would like to be able to show the solar radiation results as a colour map.

Ideally if the colour map could be created by plotting the day of the year on the horizontal axis and the solar radiation on the vertical axis.

This is driving me insane. Help would be really appreciated..

Tadgh