Or, have him step up his game by switching to a dressier button downand dont shy away from color
Women Solid Color Long Dress, Cross Halter Backless Ball Gown Cocktail Party Evening Dresses Specification Applicable Gender: Female Applicable Age Range: Adult Fabric: High Elastic Satin Color: Green/Brown/Black Pattern: Solid Color Size: S, M, L Size(cm) S Bust: 78-84 Waist: 59-64 Hip: 84-92 Length: 144.5 M Bust: 82-88 Waist: 63-68 Hip: 88-96 Length: 147 L Bust: 86-92 Waist: 67-72 Hip: 92-100 Length: 149.5 Size(inch) S Bust: 30.71-33.07 Waist: 23.23-25.20 Hip: 33.07-36.22 Length: 56.89 M Bust: 32.28-34.65 Waist: 24.80-26.77 Hip: 34.65-37.80 Length: 57.87 L Bust: 33.86-36.22 Waist: 26.38-28.35 Hip: 36.22-39.37 Length: 58.86 Note Color: As different computers display colors differently, the color of the actual item may vary slightly from the above images, thanks for your understanding

Occasion: This royal blue basque waist bodycon mini dress also can suitable for homecoming, cocktail, formal, semi formal, wedding party, prom, evening party, tea party, garden party, night out, date night, going out, birthday party, vacation, graduation, party, club, dance, birthday, or any other occasions, this dress will be your lovely partner
It's generally a relaxed business casual environment, with employees adjusting their dressy/casual levels depending on their external meeting schedules (so one person might be suited up while another is donning khaki capris)
Whether your office leans more towards business casual or creative, these denim shirt outfit ideas will help you make it work