Like stretching cling film across a doorway, transparent layers in PowerPoint provide a barrier that's invisible to the naked eye. Use transparency if you have a picture that you want to move close to the text, but it has a background colour in the way, or use a semi-transparent layer to darken or re-colour the objects underneath it. Microsoft Office PowerPoint allows you to adjust transparency in several different ways to achieve the effect you want.
Open the PowerPoint presentation in which you want to insert the transparent layer. Click on the "Insert" tab, then click the "Shapes" button. Choose the "Rectangle" shape from the list. The mouse pointer turns into a crosshair.
Click in the upper-left corner of the slide and drag to the lower-right corner of the slide to draw a rectangle, then release the mouse button. The rectangle should cover the entire slide.
Click the "Format" tab, then click the "Shape Fill" button. Click "More Fill Colors." Slide the "Transparency" slider to the right to increase the level of transparency. Setting the slider to zero per cent makes the layer opaque, while 100 per cent makes it completely transparent. Click "OK" to apply the transparency effect to the slide.
To make part of a picture transparent, select it, click on the "Format" tab, then click on "Color" and choose "Set Transparent Color." Click the colour you want to be transparent to make it disappear.