Hello Min Ji,
By default, paraview is treating the RGB components of IPFcolor as a vector, and plotting the magnitude of that vector. You need to uncheck "map scalars" to have it display all 3 components as RGB values. This option is under the properties tab in paraview.
Note that there will still be shading to give a 3D illusion, so the colors still won't exactly match the IPF triangle. If you want to do any deeper analysis beyond just visualizing the data, you should use the Euler angles or quaternions directly, not IPF color.
Regards,
Joe