I noticed that when selecting "Colour notes/CCs by track colour or by item colour" then the edges of the notes/CC were coloured differently.
On investigation, the colour used is taken from the bottom pixel of the 'channel' colours in the Colour Map (the 16 colours on the right-hand side). If you do not want them then change that part of the two rows (for non-selected and selected objects) to a neutral colour: white, grey or black.
[For info, I think that the 'Source' colour is also taken from the 'channel' colours, possible in order of creation of the clips.]