I have 3 standbys.... one is called 'Gold' from Joanne's cone thread... it is light colored and blends with any beige, light print and even light greens....the color is just weird and seems to pick up almost any light to medium shades around it....
then a light gray works for tons of stuff
and of course, any multicolored variegated thread in the tones you have used.... just open the thread, pull off several feet and lay on quilt top...it will really give you an idea of how well it enhances or disappears, whichever you prefer...