Understanding the residual tattoo ink in skin after laser treatment is often critical for achieving good clinical outcomes. The current study aims to investigate the feasibility of a light-emitting diode (LED)-assisted CMOS camera to estimate the relative variations in tattoo contrast after the laser treatment. Asian mice were tattooed using two color inks (black and red). The LED illumination was a separate process from the laser tattoo treatment. Images of the ink tattoos in skin were acquired under the irradiation of three different LED colors (red, green, and blue) for pre- and post-treatment. The degree of contrast variation due to the treatment was calculated and compared with the residual tattoo distribution in the skin. The black tattoo demonstrated that the contrast consistently decreased after the laser treatment for all LED colors. However, the red tattoo showed that the red LED yielded an insignificant contrast whereas the green and blue LEDs induced a 30% (p < 0.001) and 26% (p < 0.01) contrast reduction between the treatment conditions, respectively. The proposed LED-assisted CMOS camera can estimate the relative variations in the image contrast before and after the laser tattoo treatment.