Anonymous asked if mixing a bit of sunscreen with some foundation will give a tinted moisturiser, and if doing so will affect the SPF value of the sunscreen.
Mixing any type of foundation with a sunscreen or moisturiser will give a sort of tinted moisturiser. However, I often advise against this as, especially when mixing with a sunscreen, the pigment from the foundation often does not distribute evenly and will result in a blotchy, uneven effect.
And anything you do to dilute a sunscreen will affect its SPF, though not extremely. If you use SPF 45+, I’d say you should be fine for the day.
Does your sunscreen use chemical or physical protection? Check this before attempting this method. If it uses physical protection (like titanium dioxide), beware of being photographed. Almost all physical sunscreens result in a terrible white-cast or glare in photos, and mixing your foundation with one can produce this. Layering foundation over sunscreen can help mitigate this.
Are you looking for a sheerer application? My suggestion would be to apply your sunscreen, let it absorb for a few minutes, then apply your foundation with a damp sponge or brush. The water that is absorbed by the application tool prevents it from picking up too much product and slightly dilutes it during application, so you get a sheerer, controllable application. This also allows you to apply more product where you need it and sheer it down where you don’t. Remember, it’s always possible to sheer down a full coverage product (like Revlon Colorstay), while it’s near impossible to layer a sheer product (like a tinted moisturiser) effectively.