Add the necessary colors and/or alpha components to the theme instead. Also switch the background for ordinary channels to use the likely intended theme option, instead of the window background color. The general rule is that the channel color is drawn full strength in the channel list on the left, and with alpha in the actual key frame area on the right. This alpha is also reused with bone group colors. Reviewers: brecht, billreynish Differential Revision: https://developer.blender.org/D3813