Recent advancements in Additive Manufacturing (AM) suggest that Multi-Material Jetting (MMJ) could create materials with interactive properties that encode digital information readable by computers. However, it remains unclear if these opportunities are compatible and how they could integrate effectively in designs for tangible interaction and Extended Reality (XR). Building on the concept of Radical Atoms (Ishii et al., 2012), this research explores how MMJ might connect physical interactions with digital information through materialization. A literature study was performed to examine how multi-material 3D printing could enable XR systems to capture and interpret physical manipulation, particularly addressing challenges in XR and Tangible User Interfaces (TUIs). A unique solution space for MMJ was identified, envisioning Stimulus-Responsive materials capable of converting physical stimuli into fiducial responses for computer vision. To assess the feasibility of this embodied approach for TUIs and explore potential interactions that can be achieved, a “Research through Design” methodology was applied. The proceedings document the design and development of Colorful Bits: a Stimulus-Responsive material for kinetic interaction. Colorful Bits present a configurable Stimulus-Responsive material which captures kinetic interactions as a dynamic fiducial color response. By interlinking mechanical and optical properties through material and structure, a mechanical metamaterial is designed which transforms movement, orientation, and kinetic deformation of objects to color-encoded information. Through the physics principle of superposition, the applied stimuli that cause the movements and deformation can be obtained, allowing for force-, stress-, and pressure-sensitive interactions. By applying this process, designers are enabled to design kinetic materials for XR that provide virtual feedback in response to applied kinetic deformation. Evaluations of Colorful Bits reveal promising insights into the viability of Stimulus- Responsive materials for TUIs, though current gaps between digital models and real-world behaviors limit full application. While Colorful Bits focuses on kinetic interactions, future applications are envisioned that expand fiducial Stimulus-Responsive materials to respond to environmental stimuli such as temperature, light, and moisture, positioning MMJ as a versatile platform for XR applications.