Due to the high manufacturing flexibility offered by Additive Manufacturing, Multi-Material Topology Optimization (MMTO) of lattice structures has received considerable momentum in the recent researches. The main challenge in MMTO is to perform it without significantly increasing the computational cost, which is mostly related on the number of used materials and could controlled by using a proper material interpolation. In this work, we evaluate the behaviours of several material interpolations in conducting topology optimization of composite structures made of 28 orthotropic materials having different mechanical properties but similar costs and densities. Firstly, the materials are grouped in three families, according to their shared mechanical properties in order to facilitate the optimization process, and arranged in an interpolation domain. Secondly, a two-scale topology optimization procedure [1] is employed to conduct a comparative analysis between several material interpolation schemes, namely, the classical polynomial interpolation, classical orthogonal domain, diamond polytope domain [2], and ordered Solid Isotropic Material with Penalization (SIMP) interpolation [3,4]. Finally, numerous elasticity problems are optimized and the issues related to each material interpolation are identified.