Theoretically, there is no such thing as RGB tints. Color theory uses "tint" as any lighter hue of a color. Often this will be explained as what happens if you mix a color with white, though anyone who has spent any time mixing colors has noticed that adding white pigment changes colors in other ways than simply making them lighter.
In the commercial art world, tint is nearly synonymous with screen, because the traditional way of creating lighter shades of a base color is to print it with a halftone screen.
Because of this tradition, brand guidelines often augment a base set of colors with a subset of pastels referred to as tints or screens. This all makes perfect sense in a print-oriented world. However, when you move into digital display color, there are no screens any more. So how do we interpret brand guidelines for RGB-only software like Word, PowerPoint, Excel and the web?
Brand guidelines now normally include RGB numbers for the base colors of a brand, but tints rarely have an RGB equivalent. The designer just specs 20% of PMS 286 and lets you figure it out.