33 C.F.R. § 66.01-11
(a) Except for range and sector lights, each light approved as a private aid to navigation must:
(3) Have a minimum effective intensity of at least 1 candela for a range of 1 nautical mile, 3 candelas for one of 2 nautical miles, 10 candelas for one of 3 nautical miles, and 54 candelas for one of 5 nautical miles. The District Commander may change the requirements for minimum intensity to account for local environmental conditions. For a flashing light this intensity is determined by the following formula:
Ie = G/(0.2 + t2−t1)
Where: Ie = Effective intensity G = The integral of the instantaneous intensity of the flashed light with respect to time t1 = Time in seconds at the beginning of the flash t2 = Time in seconds at the end of the flash t2−t1 is greater than or equal to 0.2 seconds.
(5) Emit a color within the angle of 50% effective intensity with color coordinates lying within the boundaries defined by the corner coordinates in Table 66.01-11(5) of this part when plotted on the Standard Observer Diagram of the International Commission on Illumination (CIE).
| Color | Coordinates of chromaticity | |
|---|---|---|
| x axis | y axis | |
| White | 0.500 | 0.382 |
| 0.440 | 0.382 | |
| 0.285 | 0.264 | |
| 0.285 | 0.332 | |
| 0.453 | 0.440 | |
| 0.500 | 0.440 | |
| Green | 0.305 | 0.689 |
| 0.321 | 0.494 | |
| 0.228 | 0.351 | |
| 0.028 | 0.385 | |
| Red | 0.735 | 0.265 |
| 0.721 | 0.259 | |
| 0.645 | 0.335 | |
| 0.665 | 0.335 | |
| Yellow | 0.618 | 0.382 |
| 0.612 | 0.382 | |
| 0.555 | 0.435 | |
| 0.560 | 0.440 |
[USCG-2000-7466, 68 FR 68238, Dec. 8, 2003]