Car colour No (%) of cases (n=567) No (%) of controls* (n=588) Univariate odds ratio Multivariable odds ratio White 145 (25.6) 146 (25.9) 1 1 Yellow 31 (5.5) 15 (2.8) 2.0 (1.0 to 4.0) 0.8 (0.3 to 2.3) Grey 52 (9.2) 61 (10.0) 0.9 (0.6 to 1.5) 0.6 (0.3 to 1.3) Black 36 (6.4) 34 (5.5) 1.2 (0.7 to 2.0) 2.0 (1.0 to 4.2) Blue 91 (16.1) 96 (17.4) 0.9 (0.6 to 1.4) 0.9 (0.5 to 1.6) Red 85 (15.0) 82 (13.3) 1.1 (0.7 to 1.8) 0.7 (0.4 to 1.4) Green 42 (7.4) 44 (7.0) 1.1 (0.6 to 1.8) 1.8 (1.0 to 3.6) Brown 55 (9.7) 49 (6.8) 1.4 (0.8 to 2.5) 2.1 (1.1 to 4.2) Silver 30 (5.3) 61 (11.3) 0.5 (0.3 to 0.8) 0.4 (0.2 to 0.9) P value — — 0.04 0.003

^* Proportions of controls are adjusted for the cluster sampling design.

Adjusted for driver's age, ethnicity, alcohol consumption in past 6 hours, seat belt use, vehicle speed, average driving time each week, driving licence status, vehicle insurance status, and weather.