This is a version of the red border from Page 27 in black and white (actually grayscale, desaturated and darkened).
There are also a green and a brown version. To make your own version of this old page border in a different size or aspect ratio, see the notes for the Red version.
To make a diferent colour, open the image up in your favourite image editor (PaintShop Pro, PhotoShop, and the Free one, GIMP, are probably the best known). Use Colourize (it’s in the Colours menu in Gimp), set the hue to the colour you want, and increase the Lightness and Saturation until you are happy.
Another way is to select by colour, and click on a white area of background, then invert the selection, and drag a colour from the colour chooser into the selection. For the computer screen, you will want to feather the selection first, so that the edges are not jagged.