I think they weren't being highlighted at all, leading to a weird looking default white box around them.
rules:
- preproc: "\\<(ifeq|ifdef|ifneq|ifndef|else|endif)\\>"
- statement: "^(export|include|override)\\>"
- - operator: "^[^:= ]+:"
- - operator: "([=,%]|\\+=|\\?=|:=|&&|\\|\\|)"
+ - symbol.operator: "^[^:= ]+:"
+ - symbol.operator: "([=,%]|\\+=|\\?=|:=|&&|\\|\\|)"
- statement: "\\$\\((abspath|addprefix|addsuffix|and|basename|call|dir)[[:space:]]"
- statement: "\\$\\((error|eval|filter|filter-out|findstring|firstword)[[:space:]]"
- statement: "\\$\\((flavor|foreach|if|info|join|lastword|notdir|or)[[:space:]]"