Figure out what size you’re doing first, then other elements, like are you doing a spa, waterfall effects, etc. Then just scour the internet for pictures. I’ve redone an entire 4400 square foot house including a 15x30 pool (twice with the pool) and I found the pool to be the easiest to design because there are not that many different choices.

I'll give you advice from my perspective as a designer/builder when I speak with a client.

First, I ask the client what they plan to use the pool for. Is it to be a kid friendly pool with a deep end for diving? Whether or not there's a diving board.

Will it be used for just cooling off? Consider a shallow pool-say 3'-5' or 6'. Saves on heating and chemical use.

A lap pool? Generally these are long and narrow.

Shape, There's formal/modern. There's free form with perhaps water falls/features, boulder work and landscaping/plants at the pool's edge.

Once these few items are determined, you must find out what size you can put on the property based on the town/city's allowance. Setbacks from property lines limit sizes.

Your property's topography and site access can limit designs and just overall construction.

Find photos and designs on the web, magazines or a friends or a neighbor's pool you like.

Try to include the house design/architectural features in your color choices and style for the pool. It's nice to integrate the pool design with your home.

Choosing plaster finishes can be tough. Your best bet is to see a pool in person built by the contractor you choose, to see exactly what the color will look like. Same for the tile and any decking/patio choices. It's best to see all the materials in natural lighting.

Hope this gets you started.

I think choosing finishes needs to be done where the pool will be sited. Make sure you get samples that are large and place them in your lawn to help you decide among your favorites at the pool place. Actually seeing pools that your pool builder has built is a must. You will see some things you really like and others that you do not. This will be help particularly with plaster color, but keep in mind plaster color will not be exactly the same at your house since lighting and surrounding landscaping will nuance the plaster color differently. Good luck. Also be prepared for a big mess in your yard and much destruction of your yard.