Adding some pillows with color would help a lot. :)

Color. Nice selections so far but it looks pretty dismal. A few low maintenance plants in simple , maybe colorful containers. , pillows in whatever color ( s) you like.

Agree with the plants and colorful pillows. How about a colorful garden stool next to the chair and next to the sofa on the right? There are many choices in styles and colors...all up to your imagination

Woven Ribbon Garden Stool, Green · More Info

Robbins Egg Blue Circle Lattice Garden Stool ACS4508C · More Info

I like Denita's garden stool, but there is no way my behind would feel comfortable on that. Or worse, I would knock it over as I stood up.

I would use it as an end table.

Bushy green plants as Carol showed, hanging from the railing and from the ceiling, and big fat cushions in green and green print on the sofa and the chair.

If you are in some shade, you could get some coleus plants, they are great, shade of red and pink with green.

What is that big round thing covered in white?

In the photo, the white thing looks like an enormous brie cheese.

Oh loobab, that's exactly what I had intended them to be used for...as end tables! Thank you for clarifying. Sorry I wasn't specific. What's in my head doesn't always come through in my words.

Maybe a more colorful outdoor rug?

Is that a white cover over that ottoman?? You need pillows on the couch. Planters with greenery. Fix whatever is wrong with that ottoman (?) And then a few accessories. Then something very important for outside that most people neglect is lighting. Hang industrial looking string lights criss cross over the area.

If you had a party and that was your brie cheese, I'd be over in a jiff, and I wouldn't even look at your decor!

I don't think its an ottoman I suspect its something like a fire pit with a cover over it.

I think your main issue is plants. You don't seem to have any and its an outside space and needs them.

Another thought, for cushions, why not get the covers made up in a fabric that is specifically for the outdoors like Sunbrella or something like that. Then you don't have to worry about sun fade, or if it gets wet. Maybe you can even sew them yourself to save some $$. And if your ottoman is not covered in that kind of fabric, this would be a good time to get a cover like that made, or do it yourself.

If you get a cover for the ottoman made, you might want to make two, because things do get stained. If the fabric is of the type that needs to go the cleaners as opposed to in the washing machine, then for sure, you need two. (Same for the cushion covers)

Sometimes fabrics that are treated to be waterproof, sunproof can not go in the washing machine as that removes the treatment that makes them waterproof and sunproof.

I don't know if they would bother with this for an ottoman, but sometimes an upholsterer will make a mock-up pattern in muslin. If they do, you should ask to keep it, so the next time you want to make a cover for the ottoman, that will cut down on the price. After all, that particular tradesman may move or retire, etc.

As far as fabric colors, you can do whatever you like, and then again, if you have lots of green plants and other green accents, your fabric can be white or off white and you can not worry about especially treated fabric and you can throw it all in the washing machine machine and even use bleach if you need to. (Because there is always some doofus who will put their shoes or dirty hands on upholstered furniture, and by Murphy's Law the furniture is always white!)

You've got a great base! Neutral and modern, I would add planters for color and interest. I've linked some options below that would compliment your aesthetic.

Modern metal cube:

https://www.urbilis.com/metallic-cube-planter/

Railing planter:

https://www.urbilis.com/railing-planter-set/

Tall cube with color options:

https://www.urbilis.com/cubo-alto-planter/

For the sofa back

Mina Victory Damask Indoor/Outdoor Pillow, Apple Green, 20"x20" · More Info

Sunbrella Bolster Pillow, 20"x6", Macaw · More Info

We suggest colorful prints to help break up the solid colors - pillows, decorative throw, etc. If you enjoy plants, it's a great time to bring out some floral. Even a flower box that attaches to the railing or a skinnier plant with flowers would work. It seems like you have a modern style for your outdoor space, we suggest searching for pieces that complement that theme. Good luck with your outdoor room!

Agree with the accents of color and plants, but have one other thought. I immediately see privacy features. I'd be asking my husband to build a frame for outdoor curtains (but then, he's handy that way), or you can buy frames ready made, or at the very least a privacy screen on one side? If you're able you could choose and make your own curtains/screen, or simply purchase ready made in a fabric that coordinates with pillows and accessories. I think the fabric would offer some "softness" to the area, add some privacy, create color and interest, and make the space more of a "room". Nice start on your patio!