set it's background color to whatever color you want
Making a dotted (or dashed) line
Making a dotted or dashed line is a bit trickier. For full control you can use this process:
Make a flex container, and a dot zone (a text zone with no text, rounded corners, solid color) and put it in the flex container like this:
Add a caption...
Select the dot zone and hit ctrl+d to duplicate the zone til you get as many dots as you want. Note because they are in the flex contianer they will by default spread themselves in a horizontal line. (You can make a vertical line of dots by clicking the flex zone and setting the direction to be 'top to bottom'). Once you have your line of dots it will look like this:
Add a caption...
(Optional) Adjust the space between the dots via the gap property on the flex container:
Add a caption...
Tip: you can also control the size of the dots (remember you can select multiple zones with ctrl+click to select all the dot zones and resize for example).
Finally, turn off the border on the flex container and you're left with the dots or dashes: