UMLR — Location: 17.3.4 Notation Lifeline p 613 - Specification of color

Description: This clause states, “ExecutionSpecifications are represented as thin rectangles (grey or white) on the lifeline.” However, this is inconsistent with the idea that UML does not prescribe color for notations

Proposed Resolution: In place of references to color, we should stick with the convention of using the terms “hollow” to mean the same color as the diagram background and “solid” to mean the same color as the boundary of the node or the path notation. In the case of overlapping notations (e.g. ExecutionSpecifications), perhaps the spec. can prescribe patterns (e.g. cross-hatch) instead of color.

Source: Lenny Delligatti
Discussion: