Server messages using developer console?

The question is: Can I use the developer console to make those white and red server messages in chat like the "{Team} You are now on the '(Some team)' team." but custom and sent to a specific user with a specified color like red or white?

Check out this article on Chat Modules

https://developer.roblox.com/en-us/articles/Chat-Modules

The ChatService module is quite useful for messing with the chat.

You can require it like so

local ChatService = require(ServerScriptService:WaitForChild('ChatServiceRunner'):WaitForChild('ChatService'))

I would first run a game instance in studio and check out the source code to see what you can do.

Make a remote event and have a LocalScript somewhere to make the message.

In the dev console, type out game.ReplicatedStorage.RemoteEvent:FireClient(game.Players.PlayerName, Message) Replace PlayerName with the player you want to send the message to, and replace Message with what you want it to say. And replace RemoteEvent with the name of the RemoteEvent

Now, in a LocalScript;

game.ReplicatedStorage.RemoteEvent.OnClientEvent:Connect(function(message)
	game.StarterGui:SetCore("ChatMakeSystemMessage", 
	{
		Text = message; --Self explanatory
		Color =Color3.fromRGB(255, 255, 243); --Make this any color you want
		Font = Enum.Font.SourceSansBold;
		FontSize = Enum.FontSize.24;
		--Remember to end each parameter listed here with a semicolon!
	})
end)

I made the Color, Font and FontSize the default as listed on the dev wiki. If you don't list something like Font, FontSize or Color, it'll be set to default, being listed above. For more on SetCore, visit this page