In the interest of generating new biomedical sensing techniques as well as improving those that currently exist, a great deal of attention has been given to upconverting lanthanide nanoparticles in recent years. In order to develop these nanoparticles for use in multiplexed and ratiometric sensing techniques, many recent studies have focused on experimental control of their emission wavelengths. Here we describe a new method for controlling the relative intensity of green and red emission bands in NaYF4:Yb3+,Er3+ nanoparticles via control of the excitation pulse repetition rate. Using this method, particles of the same composition may be tuned to produce red and green light in user-defined ratios. We discuss the mechanism behind this control as well as potential applications that could make use of this property, specifically in super resolution imaging techniques.