System message help

color3 part isnt working. It’s in a localscript, there is no output.

How can I fix this?

The Color3 must be the value of a key called Color

Color = Color3.fromRGB(0, 161, 236)

Similar to Text and TextSize

Your properties table has the color3 value stored at a numerical index, instead of a named string index.
This is easier to see when you expand the table.

starterGui:SetCore('ChatMakeSystemMessage', {
    Text = 'aa',
    TextSize = 20,
    Color3.fromRGB(0, 161, 226)
})

You need it at a named Color index

starterGui:SetCore('ChatMakeSystemMessage', {
    Text = 'aa',
    TextSize = 20,
    Color = Color3.fromRGB(0, 161, 226)
})