Continuity mistake: At the beginning, when the Expendables and Trench are leaving the interrogation room, we see Jet Li along with his main weapon leaving with them, but in the next shot, he picks up his weapon and leaves the kitchen.
Continuity mistake: Just after Billy dies, Barney says "let's take care of him" and Toll Road puts his cap on. In the very next shot as they walk away Toll Road's cap has disappeared.
Answer: "We keep it light" refers to their mood. They joke around and tease each other and have fun. "Till we go dark" is when they get serious for killing. "We go pitch black." Meaning as dark and brutal killing machines as possible.
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