Socket LGA1155 and 1156 CPUs have an integrated PCI Express 2.0 controller, supporting one x16 or two x8 connections. The Biostar TH67XE comes with two PCI Express x16 slots, but the manufacturer, however, decided to use a different configuration, with the first PCI Express x16 slot (white) always working at x16 and the second PCI Express x16 slot always working at x1 (red). At least the manufacturer used different colors to identify the speed of each slot.
The TH67XE also has one PCI Express x1 slot and one standard PCI slot.
You can install dual-slot video cards in both PCI Express x16 slots, but you will “kill” the PCI Express x1 and/or the standard PCI slot.
It is important to understand that the H67 and P67 chipsets don’t support standard PCI slots anymore, and the PCI slot is provided by an ITE IT8893 bridge chip.