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Itching and discoloration of the genital region can be due to fungal infections (Tinea Cruris, ringworm) also called Jock Itch. Other causes of genital itching can be due to allergy,skin friction Eczema, and bacterial infections.
You may consult with your doctor for a examination and undergo proper treatment for the specific conditions.
The following tips may prevent such issues from occuring:-
1. Wash your groin daily, then dry thoroughly. Drying is perhaps the most important point. (A hairdryer is useful if you have hairy groins.)
2. Change underwear daily.
3. Avoiding use of excessive force and friction during masturbation would also be helpful.
4. Avoiding soaps, and hygiene products containing synthetic or harsh chemicals.
I hope this helps.