An aesthetics idea rather than chemical functionality
It would be nice to be able to change a colour without selecting the bonds/molecules. Say you had a handful of molecules and in each one a single bond was red. It would be nice to be able to change all red items on the page to a different colour without selecting each bond (i.e. click the colour red and tell ChemDraw to make that colour purple)
Gareth, you are right.
I submitted a huge report on "Find and Replace" Highlight or Ring Fill colours" feature last year:
https://chemdraw-20-beta.ideas.aha.io/ideas/CDBETA20-I-31
My point was not aesthetics, but necessity: if you have 10 files with pink used as a highlight colour and you need to change it to blue, you need to do a lot of monkey work. As a hack, I was exploring a way to manually alter data in <colortable> in cdxml-file. But it a mess, it's extremely difficult to identify colours there, as no name tagging are used and colour order is not fixed:
<color r="0.9020" g="0.0353" b="0.7255"/>
I offered a lot of sound ideas how to make life around colour data easier (HTML name tags for colours, hidden parameter, pre-defined order for all colours in the <colortable>), but... Introducing of Ring Fill colouring and Bond/Atom Highlighting functionality in v20 missed on many points, that still need to be addressed.