I don’t actually have “A” specific color that I use. Here’s what I do. I buy a color that is closest to what I want, then I add a little light green or sometimes some additional aqua, or light blue or gray or white . . . .whatever strikes me at the time. So the color evolves as I work my way through various projects. I actually PREFER to not have every item the EXACT same color. The variations in shades remind me of the ever changing colors of the ocean.
Every paint manufacturer whose paint samples I’ve looked at lately has a least one (if not several!) color that is very close to what I use. So, it shouldn’t be hard to find one that suits you. As for changing the color by adding other paint colors, regular craft paint can be used in small amounts if you don’t happen to have latex paint available. You can also look for the ‘oops’ paints that paint stores sell really cheap!
I AM a stickler for only buying Ralph Lauren brand paint though whenever possible. (at least for my MAIN colors) Tried others when they were on sale and have always regretted it. The RL paint IS quit a bit more expensive to BUY; but it’s so cost effective to USE, you really come out ahead. Especially if you are doing a LOT of painting, like me!