"Lighter tone" means to have a more relaxed and cheerful atmosphere or manner of speaking, contrasting with something serious or heavy. Full definition
In the 50's our home looked like the set from an early Mad Men episode... orange vinyl sofa, Danish inspired chairs, sleek wood pieces in light tones of wood. (theinspiredroom.net)
A light camel gives a softer look and should generally be matched with lighter toned clothing. (theidleman.com)
I'm making an effort to add in lighter tones with my budget this month! (viewfrom5ft2.com)