If the global colour / color scheme is applied to a space, and the global scheme is updated, the changes are reflected immediately in Administration. However the space colours are not updated until Confluence is restarted.

To replicate:
1) Go to a space which has the global colour scheme selected under Browse Space > Space Admin > Colour Scheme
2) View the space homepage,
3) Go to Administration > Look and Feel > Colour Scheme
4) Edit the colour scheme and save. Colours are updated on the administration screen.
5) Refresh the space homepage. No changes.

Restarting Confluence updates the space colour scheme.