The Colors of Halloween: PowerPoint Background
Why are black and orange the colors of Halloween?
Because
black implies the growing darkness of October? (and Daylight Saving Time ends only a few days before Halloween this year, making our autumn evenings even darker?)
Because
orange implies the color of harvest? (Think of golden leaves and fat orange winter squashes like pumpkins and hubbards?)

For an
abstract PowerPoint background that uses the colors of Halloween without knocking you over with graphic, scary images of cobwebs and bats and haunted houses and ghosts (oh my!), you can apply simple colors and shapes to make your October PowerPoint presentations more seasonal.
Try the abstract
pumpkin PowerPoint background, for example.
Here's how: Click on the above link, then right click on the image, and then Save Image As... Next, apply the background image in PowerPoint by clicking
Format>Background>Fill Effects>Picture -- then select the picture and click
Insert>OK>Apply.)
Happy Halloween, Pumpkin!