Thin men are often the best ones that can apply the newest trends in fashion. To some real extent, most models are thin. But for some body type, clothing design must be appropriately chosen regarding what kind of situation you are in or what kind of job you are having.
Choosing light colors will give you an additional weight by your looks, not the actual weight though. Wearing lighter colors seems to expand your body mass rather than wearing dark color or tones which tend to shrink your size, so choose bright colors.
If you want to wear dark colors, make sure that you have light colors that you can layer with. Do the alternative, if you want to wear fairer of lighter colors, you can layer them with dark colored clothes. This will even up everything and will not give you the look that exalts your exact physique.