Our research group has investigated various kinds of soft mechanisms for many years. Through these researches, several soft rubber actuators driven pneumatically have been developed. The typical one is FMA (Flexible Microactuator), which realizes continuous bending motions like a human finger. In addition, we are recently interested in several novel functions appeared on soft mechanism surfaces such as repellency, hydrophily, friction, structural color, and adhesiveness, which are realized with micro scale soft structures fabricated on the surfaces. We believe novel additional functions can be realized by utilizing the deformability of the soft structures. In this paper, micro grating structures made from silicone rubber are reported. Because of its elastic property, it can realize changing structural color. The experimental results show that beautiful color change can be observed. We fabricate a soft micro grating structure on FMA and confirm the appearance of structural color, which changes in following FMA's motion. This color change indicates distributed information of the strain of FMA, which may be used for servo control of FMA in the future.