CLCT items can be used in the same way as other data with no specific license terms. You can edit or add textures, and change parameters however you like.
For more details, please refer to the VRoid Studio Guidelines or the VRoid Studio Terms of Use.
For more information on CLCT, see the Help section below.
▼What is CLCT?
https://vroid.pixiv.help/hc/en-us/articles/17425738214041