Double-flowered Eustoma, a popular cut flower, sometimes shows nonuniform coloration of its petals when harvested at the flower bud stage. At the tips of the petals, pale greenish areas remain after the flowers open. This considerably reduces the value of cut Eustoma. In this study, to identify appropriate postharvest treatments leading to normal coloration of these cut flower buds, we investigated the influence of harvest stage, temperature, sugar, and methyl jasmonate (MeJA) on petal coloration using the Eustoma 'Voyage (Type II) Blue'. Investigation of the harvest stage, which was compared at three flower bud stages (STG2, 3, and 4), revealed that detached pale greenish flower buds (STG2 and 3) had a high probability of becoming nonuniformly colored flowers, so these stages were used for subsequent investigations. Temperature, which was investigated at 20, 25, 30, and 35 degrees C, did not show any influence on petal coloring. Investigation of sugar treatments, such as 1% or 3% glucose or sucrose, also showed no influence. However, MeJA treatment led to a significant difference in petal coloration. The nonuniform coloration of petals was reduced by continuous exposure to MeJA vapor. Furthermore, we performed shorter MeJA treatments, such as for 1 or 2 days after harvesting, which reduced the nonuniform coloration as well as continuous MeJA exposure. To evaluate the effect of MeJA treatment on petal coloration, we measured the rate of pale green areas of petals using digital images. The analysis revealed that the greenish areas in petals exposed to MeJA vapor were significantly smaller than in petals not exposed to MeJA. In addition, there were fewer days to flowering after MeJA treatment. We concluded that postharvest treatment with MeJA is effective for reducing nonuniform coloration of early harvested flower buds of the double-flowered Eustoma 'Voyage (Type II) Blue'.