The shirt is a debatable area. If it’s the corporate world, go with something solid, a brighter shade shirt in most cases is acceptable. No I don’t mean neon purple, unless it’s Halloween no one’s going to take you seriously looking that “jovial” strolling into your interview. Remember, is the neon purple shirt you wore because you hoped to “stand out” going to take it home? Or 9 times out of 10 will it be the guy that decided to go with a calm navy blue? So, if you go a little lighter on the color, knock yourself out, but don’t go nuts.
Long sleeve looks sharp anytime of the year. I’d recommend it always. Otherwise how will you wear a tie?! But, if it’s summer and 100 degrees out, most employers will understand if you wear a nice dress, short sleeve shirt.