Adobe Illustrator has some nice colour tools, one of them is the Color Guide, that you can use to create a good colour palette for your science visual or science poster. Here I will describe step by step how to do this.
Open your Adobe Illustrator file.
Pick a colour (any color you like, that is suitable for a science poster) in the left icon menu:
Go to the top navigation bar > Window > select Color Guide. The Color Guide menu appears on your screen:
The color guide shows various colour palettes, with your selected colour, in the dropdown menu:
The menu in the top right corner of this Color Guide panel offers more colour options, such as generating tints and shades, editing your colour palette manually, warm and cool colours and muted and vivid colours: