Instructions
Launch "Team Fortress 2."
Click "Options" on the main menu, followed by the "multiplayer" tab. The options for the crosshairs are located on the top half of the "multiplayer" tab.
Click the drop-down menu under "Crosshairs Appearance" to customize the look of your crosshair. For example, you can change your crosshair to a cross or to a small dot.
Use the "Size" slider to change the size of the crosshair. Slide the bar to the right to make the crosshair bigger and to the left to make it smaller.
Use the color sliders (red, green and blue) to change the color of your crosshair. Your crosshair is shown to the left of these sliders and you can view the changes to your crosshair in real time.
Click "Apply" to save your changes, followed by "OK" to exit the menu.