Mustard (#FFDB58) is a very light, highly saturated yellow hue. Mustard yellow is warm and slightly muted, a mid-century and autumn favourite.
In RGB it is made of 255 red, 219 green and 88 blue. Its HSL hue angle is 47° with 100% saturation and 67% lightness, while its perceptual OKLCH lightness is 90% with a chroma of 0.151. For print, a starting CMYK mix is 0% cyan, 14% magenta, 65% yellow and 0% black.
As a text color on white, Mustard has a contrast ratio of 1.35:1, which fails WCAG AA even for large text. On black it reaches 15.53:1 and passes AA for normal text. If you use Mustard as a background, put black (or very dark) text on it. The APCA lightness contrast is Lc 86 for black text and Lc -20 for white text.
Its perceptual complement is #D3DCFF, close to lavender. Colors that look most similar are gold, lemon, amber. It looks fairly similar to people with red-green color blindness (ΔE 2), so its meaning mostly survives.