My Ti plants are notorious for attracting aphids in the early spring. I would check for those first. Sometimes they are down in the furled leaves just coming out too. One other thing could be too much water. Sometimes the colors are not as vivid in the winter either, I think due to lower humidity dries out the leaves a little.
Maybe someone else can add some other ideas too.

Besides aphids, mites dote on Ti's..Especially during winter months..dry air and constantly wet soil will cause problems..Besides humidity, they require a room with air circulation.. Toni

My ti are all mealybug magnets!! Its like they have a sign on them that says:
ALL MEALYBUGS, LAND HERE

LOL bihai, that's exactly how I feel about the mandevillas..mealy bugs *love* them!! They get all into the little vines and crevices drives me nuts I literally have to tip them over (pots)and drown them in NEEM. The mealys dont bug the Ti's with the mandevillas around maybe you should plant some next to the Ti's (snort):P

Oh those mealy..They're the worse. Several ppl on the Hoya forum suggest using fragrant geraniums..crush a leaf and scatter over soil for plants that tend to attract mealy..It might just work, and worth a try. Toni