I have same issue and there are simillar issues with plymouth 0.9*.
The sites below are related with this problem. But these weren't worked for me.
https://forums.gentoo.org/viewtopic-t-1067912-highlight-plymouth+text.html
https://forums.gentoo.org/viewtopic-t-1073844-start-0.html
https://bbs.archlinux.org/viewtopic.php?pid=1742556#p1742556