Conservation treatments may cause alterations to the aesthetic qualities and appearance of paper materials, including their color. The scientific evaluation of color change to measure the effects of conservation treatments is therefore valuable information for the conservator weighing the advantages and disadvantages of the various treatments and approaches available. In this study, two Japanese tissue papers (Yukyu-shi and Sekishu Mare) were treated with plant dyes including black tea, henna, fresh and dried Eucalyptus cinerea leaves, as well as selected watercolors and acrylic paints. Paper specimens were subjected to both moist-heat artificial aging and accelerated photo-aging and color changes were measured using spectrophotometry and microfading tests. Color change is here defined as a change in light/dark, red/green, and yellow/blue coordinates in the International Commission on Illumination (CIE) color space of light reflected from a colored surface before and after an intervention such as accelerated aging. The findings of this study show that paper samples treated with plant dyes experienced larger and more perceptible color changes, as measured by spectrophotometry, compared to untreated controls and samples treated with watercolors and acrylic paints. Thus, plant dyes have poor color stability after moist-heat aging when compared with watercolors and acrylic paints. Nevertheless, papers treated with alizarin crimson acrylic paint, dried eucalyptus leaves, and black tea exhibited minimal color change after photo-aging. This study provides paper conservators with a better understanding of toning materials and their color stability when chosen for paper conservation treatment.