@pipingguy said:
OK - here is my understanding:
To modify a color in a custom collection:
Tools menu > Paint Bucket.
Display the secondary pane by clicking the icon directly below the exit button.
In the secondary pane, scroll thru the drop-down list and choose the custom library.
In the primary pane, scroll thru the drop-down list and choose the “In Model” library.
Or, if you're lazy, click on the little house icon to the left of the drop down list.
@pipingguy said:
In the secondary pane, right-click the color icon that you want to adjust and pick ‘Add to model’.
Said color icon now appears in the Model Library; click it and then click the Edit tab.
Adjust color and/or transparency……also rename if you wish.
Click the Select tab
Drag the color icon back into the Custom Library and choose ‘overwrite’ when prompted.
No need to do anything else. You can exit SketchUp without even needing to save the drawing.
The modified color will appear in the Custom Library when you re-start the program.
Note- if you change color transparency, do not expect the color icon, when it’s displayed in the custom library, to show the two-tone diagonal slash as normally shown in non-custom palettes.
That's pretty much it. I'd never saved a color with transparency before so never noticed but you're right about the thumbnail. Maybe there's a way to change that, though.