Is it just in one view? The issue could be that the graphics were overriden. Check "override graphics in view" by right-clicking on one of the objects with the color issues.

There are only about 4 possibilities with this problem.

1. as Gigi mentioned, someone has over-ridden the graphical representation in that view either by element, or by category.
To fix this, select the beam and right click, then select "override graphics in view" --> "by category" and reset any changes made.

2. The view template has changes to it. To see this, in the view type "VG" and scroll down to "structural framing" and see if there are any changes made to color here.

3. A view filter has been added. To see this, in the view type "VG" and along the tabs at the TOP of the dialogue box, look for "Filters" click on the filters tab and you will see if any over rides have been made. If there is nothing present in this tab, then no over rides are made.

4. Material appearance has been changed. As you already eliminated this as a possibility, you can move on to testing out the other 3. I would personally eliminate them in the order I listed them here.