Ignore "transparent" color keyword

The upgrade to 3.3.0.rc.1 resulted in a bug where `ColorKeyword` would
report lints for using the "transparent" keyword. This was caused by
"transparent" being added to the list of `COLOR_NAMES`.

Change-Id: Idab10be0b8028b238d65548804fa9f989bf66776
Reviewed-on: https://gerrit.causes.com/30178
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>