There are a few steps you can take to attempt to correct this issue:

1. Check to make sure the color is still visible in the Color palette:

   Once inside the PowerPoint presentation, select the Design tab. Check near the right side of the screen for the Colors palette. Ensure that the color is still visible.



2. Verify the color is selected on the slide you are trying to view:

   Using the same Design tab, select the Slide Background option. Click on the Format Background option. Select the Fill tab in the new window that appears. Verify that the correct color is selected next to Solid fill option.



3. Check the Transparency setting of the slide:

   Select the Design tab again. Check near the right side of the screen for the Slide Background option. Click on the Format Background option. Select the Picture or texture fill tab. Select Recolor and verify that the Transparency is set to 0%.