Studio accepts hex values for Color3 properties, but seems to set their value in RBXLua Color3 format, which uses percentages (0 to 1) for RGB instead of the normal 0 to 255.
For example, entering “#000000” sets a color to “0, 0, 0”, and “#FFFFFF” sets a color to “1,1,1”. If Color3s in studio used percentages (such as how it is done in RBXLua) then this would be fine. Instead, this sets it to almost-black, since studio uses a 0 to 255 format. This sounds like an easy fix that just needs to multiply the values by 255 before settings them in the property.