Answer:
AGEB
(assuming its in the order of the lock colors in the corner of the picture)
Explanation:
Slope Intercept equation: y=mx + b
m : slope, can be found by rise/run
b: y-intercept, where the line intersects with the y axis
Red Line: b: -1, m: rise 3, run 1 (3/1=3)
equation: y = 3x - 1
Orange Line: b: 4, m: rise 1, run 1 (1/1=1)
equation: y = x + 4
Green Line: b: 2, m: rise -2, run 1 (-2/1=-2)
equation: y = -2x + 2
Blue Line: b: 2, m: rise -1, run 2 (-1/2= -1/2)
equation: y = -1/2x + 2
The letters that fits all of the equations are A (red), E (orange), B (green), and G (blue).
If the code goes in order of the colors at the bottom, then it should be AGEB.