In the Theme-node under settings you can change colors, fonts, logos and much more.
By default Igloo uses Roboto Font. To change this first change the Embed Font under Theme -> General.
Next change the font stack on Body Font & Heading Font
To change the color pickers to match the site branding go to Developer / Data Types / Color pickers. Remove the last color from IG - Background - Approved Color and IG - Theme - Approved Color and add the new color. Do not change the black and white colors.
For a list of UI-elements go to https://demo.iglootheme.com/ui
or write /ui in your installed Igloo (only version 1.4+)