California has a diverse climate and soil types, so the best pasture grass seed for the state will depend on the specific region and the desired use of the pasture. Some of the most common pasture grasses grown in California include:

1. Bermuda Grass: This warm-season grass is widely used for grazing and hay production in the southern and central regions of California. It is drought-tolerant, and can handle heavy grazing pressure well.

2. Fescue: This cool-season grass is well-suited to the cooler coastal regions of California. It is used for grazing and hay production, and is known for its high-quality forage.

3. Orchardgrass: This cool-season grass is widely used for grazing and hay production in the northern and central regions of California. It is known for its good forage quality, and can be grown in a range of soil types and climates.

4. Ryegrass: This cool-season grass is used for grazing, hay production, and erosion control in California. It can be used as a cover crop and can be planted alone or in mixture with other grasses and legumes.

5. Brome grass: This cool-season grass is used for grazing and hay production in California. It's known for its high forage quality, high yield and tolerance to drought.

It's important to note that the best pasture grass seed for California will depend on the specific conditions of the land, including soil type, climate, and intended use of the pasture. It's recommended to consult with a local expert or agronomist to help determine the best grass seed for your specific needs.