What is the color of the vehicle that is pulling a train?
The train engine is yellow.
    src        edge_attr  dst
0     0          pulling    6
1     0   to the left of   11
2     0  to the right of   15
3     0  to the right of    3
4     1               of    2
5     1   to the left of    4
6     2   to the left of    4
7     3               by    4
8     3             near    4
9     3      in front of   14
10    3             near    7
11    3   to the left of    0
12    3             near   12
13    3   to the left of    6
14    3   to the left of    8
15    4  to the right of    2
16    4  to the right of    1
17    4             near    3
18    6               on    4
19    6        pulled by    0
20    6  to the right of    3
21    6   to the left of   11
22    6     traveling on    4
23    7             near    3
24    8  to the right of   15
25    8  to the right of    3
26    8   to the left of   11
27    9               by    3
28    9   to the left of   11
29   11  to the right of    9
30   11  to the right of    0
31   11  to the right of    8
32   11  to the right of    6
33   12          next to    3
34   15   to the left of    8
35   15   to the left of    0