Abstract: Visible Light Communication (VLC), a candidate technology of sixth generation (6G), offers access to a broad license-free spectrum, a higher level of security, and protection from radio frequency (RF) interference, making VLC an effective complementary solution to RF communication. With these features, VLC serves as an effective complement to RF communication. VLC systems are primarily designed for indoor scenarios, with typical transmission distances ranging between 2 and 5 meters. In wireless networks, reconfigurable intelligent surface (RIS) have recently demonstrated a significant impact. This paper introduces indoor power domain non-orthogonal multiple access technology (PD-NOMA)-based VLC downlink communication system, designed and optimized to include a simultaneous transmitting and reflecting RIS (STAR-RIS) in the channel and a liquid crystal (LC) RIS-based receiver with co-assisted composition. That is the STAR-RIS under the energy splitting (ES) protocol is deployed in the transmission channel, and LC-RIS-based VLC receivers are employed at the receiver side, both schemes having the effect of enhancing the optical signal. To evaluate the proposed system's performance, a sum-rate maximization problem is formulated and solved. This maximization problem accounts for practical situations such as the presence of non-user-obscured line-of-sight (LoS) paths between the transmitter and the receiver. A low-complexity algorithm is recommended for the perfect channel state information (CSI) setup. This algorithm obtains the optimal solution for the joint design problem by utilizing the fractional programming (FP) technique and step-by-step optimization scheme. Due to the non-convexity of the objective function, the objective function is first transformed into a multinomial fractional planning problem using the Lagrangian dual transform to make the objective function more tractable. Secondly, the step-by-step optimization scheme and the CVX tool are used to obtain a feasible solution. Additionally, this paper analyzes the effects of the number of light emitting diodes (LEDs), the wavelength of the optical signal, and the refractive index of LC on the performance of indoor visible light communication system. The final numerical simulation results show that the sum rate of the indoor VLC system assisted by the combination of STAR-RIS and LC-RIS is significantly higher than that of the VLC system with only reflective RIS and no LC-RIS under the ES operation protocol, nearly 130% increase in system sum-rate. Additionally, the number of LEDs, the wavelength of the incident light, and the refractive index of the LC all affect the system performance to some extent. These findings provide an important reference for the design and optimization of indoor visible light communication systems.