Using the two-color counter model, we can visualize subtracting integers when the starting collection has enough counters of the correct sign to naturally remove.

• To model $6 - 4$, start with $6$ positive (blue) counters. Removing $4$ positive counters leaves exactly $2$ positive counters, confirming that $6 - 4 = 2$.
• To model $-6 - (-4)$, start with $6$ negative (red) counters. Removing $4$ negative counters leaves exactly $2$ negative counters, confirming that $-6 - (-4) = -2$. Both calculations demonstrate the straightforward take-away method that applies when the minuend and subtrahend are represented by the same color counters.