What does the red candle signify?

The red candle represents the fate from which the mothers have escaped, that of being bound by what others want for them. Both Lindo and Ying-ying were expected to be quiet and "dark," not expressing their own opinions. They grew up in a society that urged them to forget their own desires; any wishes they had were sinful by definition. Like the Moon Lady, they would be punished and shamed for taking what sweetness they wanted out of life. This made them begin to disappear, to depend on others for illumination while finding only darkness within.