Complex sentence: The contract insisted on the huge size (to cover 66 square meters), and that the quality of pigment and colors should be of premium quality, for example the blues should contain the precious mineral lapis-lazuli.
Split into simpler sentences: The contract insisted on the huge size (to cover 66 square meters), and that the quality of pigment and colors should be of premium quality. For example, the contract specified that the blues should contain the precious mineral lapis-lazuli.