What color vest is best formal and streetwear?

[elliottchow]

Would like to know what color vest would be best for both casual (eg: with tshirt) and more casual occasions with (dress shirts). What type of material would be best for hot weather? 28 degrees and over? Lastly, are there any differences in design for vests that are made for streetwear and formalwear?

 

[Klobber]

cotton. color = summer colors.