All drawing must occur in a Draw event.
When the Draw event is added to an object, GameMaker no longer automatically draws the instances sprite. Since this is not a traditional parent event override, we cannot use event_inherited(), but GameMaker did provide draw_self().
GameMaker can be seen as utilizing an engine to perform drawing. For this reason, functions are provided for modifying the configuration of the engine as well as commanding its actions.
For example, to draw a text of a certain color, the engine must first be configured:
draw_set_color(c_red)
draw_set_halign(fa_left)
Only then can the engine be commanded to draw the desired result:
draw_text(x, y, "Left aligned red text")
Use c_[color name] to access most colors.
Can a variable's value change from a number to a word?
Learn More:
Strong and weak typingGameMaker Manual - What is Programming
Wikipedia - Strong and weak typing