it is inefficient to allocate a tiny object like Color separately on the
heap

Change-Id: I2f03538f987ff032857f3316ed2d8c2c8d731549
Reviewed-on: https://gerrit.libreoffice.org/67968
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>