The yellow powder and the blue liquid producing a clear green liquid after mixing shows that these two substances are soluble.
The soluble substances are those which are completely mixed in each other producing a new solution. The insoluble substances are those, which do not mix together with each other, and remain separated. The miscible substances are those liquids which completely mix with each other forming a homogeneous mixture, while the immiscible substances are those liquids that do not form a homogeneous mixture when mixed.
Hence, the answer is 'soluble'.
