Jean jackets or any dark colores jacked! Light with light doesn't blend that's why u find ppl or wearing dark shirt and light jacket or sweater..or a light shirt and darker jacket..good colors that go with anything would b navy blue, dark grey, black and white since ur shirts r light...if u have a dark pink (not to light) ten a light gray will b perfect for it..just try buying basic colors that go with anything (like the ones I mention before) DO not wear a yellow shirt and white jacket! That will not look good or with light gray..it would look perfect with dark gray..now if ur blue shirt r really light then buy a dark gray or blue jacket...if some r kinda darker tone of light blue then still use a darker blue sweater..
If you are looking for design ideas to print yourself, cheaper and better.
The popular 'Broderbund' software company has tee shirt printing software called T Shirt Design Shop. This is low cost tee shirt printing software that provides over 4,000 graphics; 1,000 layouts already designed; 75 fonts; photo and text effects; and photo editing tools. Hope that helps.