If it is truly DOT fluid then 49 CFR § 571.116 - Standard No. 116 dictates:
S5.1.14 Fluid color.Brake fluid and hydraulic system mineral oil shall be of the color indicated:
DOT 3, DOT 4, and DOT 5.1 non-SBBF - colorless to amber.
DOT 5 SBBF - purple.
Hydraulic system mineral oil - green.
Dark brown is not generally considered the same as "amber".