Sometimes the issue is not a leak but rather the overflow system discharging excess fluid (which is normal). I found this out after taking my car to the dealer to figure out why I was seeing some blue fluid on my car on a hot day. This only happened after I topped off the fluid in the reservoir (so the heat caused the liquid to expand).
Daily Driver: 2005 Lexus LS430
Fun Car: '11 E92 M3 6MT w/ M. Perf. Exhaust
Prior (all 6MT): '06 330xi, '09 135i, '11 550i, '13 335i