Use the edge of the area, not its unpainted interior
IFAB Law 1 makes boundary markings part of the areas they enclose. A location on the penalty-area line is therefore not automatically outside merely because it is on paint rather than grass inside the rectangle.
Imagine a direct-free-kick offence occurring precisely on the outer painted edge of the penalty-area line. A freeze-frame showing the contact on white does not support the claim that it must be a free kick outside. The line’s membership is the relevant geometric fact.
The player’s feet are not always the offence location
A wide view may show most of a player’s body outside while the relevant contact happens elsewhere. Identify the offence’s location before comparing it with the marking. This article explains the line; it does not decide every incident involving a moving player or a continuing hold.
A useful replay includes the actual contact point and the full width of the painted line. Drawing an imaginary boundary along its inner edge would shrink the area incorrectly. Keep that distinction in mind when a studio graphic appears close to the paint: the drawing must represent the correct edge rather than whatever side is easiest to see.
Questions answered
Is paint automatically outside the area?
No. The boundary line belongs to its area.
What should I locate before discussing the line?
The relevant offence, rather than only the player’s overall position.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.