Flexible chemical sensors utilizing chemically sensitive nanomaterials are of great interest for wearable sensing applications. However, obtaining high performance flexible chemical sensors with high sensitivity, fast response, transparency, stability, and workability at ambient conditions is still challenging. Herein, a newly designed flexible and transparent chemical sensor of reduced graphene oxide (R-GO) coupled with organic dye molecules (bromophenol blue) is introduced. This device has promising properties such as high mechanical flexibility (>5000 bending cycles with a bending radius of 0.95 cm) and optical transparency (>60% in the visible region). Furthermore, stacking the water-trapping dye layer on R-GO enables a higher response as well as workability in a large relative humidity range (up to 80%), and dual-mode detection capabilities of colorimetric and electrical sensing for NH3 gas (5-40 ppm). These advantageous attributes of the flexible and transparent R-GO sensor coupled with organic dye molecules provide great potential for real-time monitoring of toxic gas/vapor in future practical chemical sensing at room conditions in wearable electronics.