@djpawl
My solution for Police: 3:01, 43 parts.
Using green to keep track of string endings and moving two yellows towards eachother from both ends. Your solution sounds like it could be quicker tho if executed correctly.
?lvl=19&code=g12:2f3;y12:3f3;r11:4f2;p12:4f7;b13:4f0;y12:6f3;q12:5f0;b9:8f2;c9:9f1;c9:10f1;c9:11f1;c9:12f1;c9:13f1;q10:7f5;p10:8f5;y10:9f2;q10:10f6;p10:11f4;q10:12f2;y10:13f0;c11:9f1;r11:10f3;c11:11f0;b11:12f1;c12:7f2;b12:8f2;b12:10f3;y12:11f0;r12:12f2;g13:7f3;p13:8f3;q13:9f2;p13:10f3;i13:11f6;p13:12f7;q13:13f1;r14:8f0;r14:10f3;c14:11f0;b14:12f0;y14:13f0;r11:8f0;c11:7f2;
 "Manufactoria"){kind=icon}