My best advice is 'Gigantic futanari' LoRA https://civitai.com/models/18343?modelVersionId=589632 ! It's also for Pony models, and biases strongly towards light penises, even on darker-skinned bodies. (It's also conveniently much better designed and implemented than this model!)

If you're still looking for a resource for lighter-skin-tone cocks, while it's true that I still recommend the 'Gigantic futanari' LoRA in my other reply—my new LoRA that guides huge cocks of a more general variety is now out! https://civitai.com/models/931695 Let me know if you get any good results with it, it's unfortunately pretty reliant on stronger anatomical models or body-guiding LoRAs, but it should help with huge cocks of any color!