With the rise of renewable energy in electricity generation, new electricity market trading mechanisms that consider the inherent intermittency and environmental contribution of renewable energy should be developed. Typically, renewable energy generation facilities are located in areas with low electricity loads, leading to potential power abandonment. Cross-regional power transmission is expected to be an effective method to improve the energy use efficiency of renewable energy. Notably, cross-regional electricity trading of renewable energy can help reduce pollution emissions and electricity generation costs in receiving regions, which makes it become attractive to the receiving regions. However, in practice, the regions with abundant load supply hesitate to participate due to a lack of appropriate profit-sharing contracts. Moreover, the intermittency of renewable energy generation, which affects the stability of electricity supply and the willingness to purchase in receiving regions, is also a concern. Motivated by these practical challenges, we aim to design appropriate contracts for the cross-regional electricity trading. Firstly, a green-contribution-based revenue-sharing contract, which benefits the supplying region, is designed to allocate the cost savings resulting from purchasing renewable energy. Secondly, a supply flexibility contract, which determines a two-tariff price for promised electricity supply and flexible supply, may prevent the receiving region from the negative effects of uncertain power supply. Finally, we design a new contract that considers both of the above contracts to investigate whether a win-win situation for both the renewable energy generator and the retailer exists under specific conditions.