Based on the level of respect or formality, you can say "My hobby is paintball" in Korean in 3 ways:

• Informal: nae chwimi-neun peinteubol-iya (내 취미는 페인트볼이야)
• Formal: nae chwimi-neun peinteubol-iyeyo (내 취미는 페인트볼이예요)
• Very formal: je chwimi-neun peinteubol-imnida (제 취미는 페인트볼입니다)