Stroke (Both) adds color to both sides of the drawn line.
Prepare an illustration you would like to add borders to.
Open ①the Layer window, and select ②the current layer and drag over the layer that contains the image you would like to apply the filter to.
From ①the Tool Selection window, select ②Filter.
Select ①Stroke (Both).
Drag ①the sliders left and right to adjust the width of the borders.
Drag ①the slider left and right to change the color of the borders. Tap ②✓.