Thanks Eric, most helpful!
It was the ManageIQ logo for the login and top Nav Bar, but we just replaced instead with another SVG. We did try amending some of those colour codes previously, but must have missed a step.
In terms of Title the bit we wanted to change was:
title = I18n.t('product.name')
But looks like amending that will cause other issues, so we will leave that well alone and leave it as "ManageIQ" ( just trying to appease the marketing department ).