Color space conversion is very important in many types of image processing applications including video compression. This operation consumes up to 40% of the entire processing power of a highly optimized decoder. Therefore, techniques which efficiently implement this conversion are desired. This paper presents four different scalable architectures for efficient implementation of two such color space converters using an FPGA based system. Distributed arithmetic technique and systolic design have been exploited to implement the proposed structures on the Celoxica RC1000-PP FPGA development board. The implementation approaches exhibits better performances when compared with existing implementations.