Distribution of our radio star samples with the reference background. In the upper right legends of all four panels, we show the reference background of main sequence stars, subgiants, red giants, and supergiants from the works of Berger et al. (2018), Bowman et al. (2019), and Spetsieri et al. (2019), respectively. In the bottom-left corner, we provide the corresponding subclassification legend for this study (i.e., single stars, binary stars, and different evolutionary stages in both samples). The stars in both samples are distributed across various evolutionary stages, and for Sample 2, the radio-bright stars are predominantly located in the low-temperature main sequence.