Step-by-step how to do this yourself:
1: Download this mod list: https://www.nexusmods.com/cyberpunk2077/mods/521
2: Open Tweak Browser in WolvenKit.
3: Use the document from step 1 to find a weapon, example Guts (items.preset_carnage_edgerunners).
4: Type in the Tweak Browser of WK, "items.preset_carnage" and you'll find Guts.
5: Right click one version, like the Edgerunners, and "add TweakXL Override". That should add the file on left side of WK.
6: Open the file called "Items.Preset_Carnage_Edgerunners.yaml" and search for "visualTags".
7: Below "visualTags" is the item variant it will appear as. Example, on Guts it will say:
visualTags:
- Edgerunners_Carnage
So if we change "Edgerunners_Carnage" to "Neon" it will spawn Guts with Neon skin variants. I got the Neon variant from using the document on step 1 and searching for "Carnage". Since Carnage is the non-iconic weapon, it has more than 1 skin variant. I used the weapon ID from that list to search for it in WolvenKit and like Guts, find the VisualTag for that item, which in this case is "Neon".
Hopefully that makes sense! Otherwise, I can scrabble together a visual guide.