With the stripes faded, each red line runs straight across both sides: one red.
Tricks of color
Bezold effect
Which red is lighter, left or right?
Neither: it is the same red, though the left looks lighter and pinker.
Why? With thin lines, colors blend together instead of contrasting. Weavers and painters have used this for centuries to change colors without new dyes.
Picture: Lockal, Public domain · Wikipedia(opens in a new tab)