Switch on the grid
Create a rectangle
Press F2 and grab the circle grip and drag to make it rounded
Make another rectangle , fill it with white and a gradient from white to transparent
Switch of the stroke
Copy the original rectangle and lower to bottom
Change it's color , switch of the stroke and add transparency
Add some text
Export as a png
You can change the color of the first rectangle and get a variety of colors.
The svg file can be downloaded here .