The color page of the sound production manual on this website describes how to create a synth of a particular color with FL Studio built in 3x Osc. If you want to calculate the volume values for each oscillator on the synth faster and easier you can try 3x Osc color calculator. It’s a simple free and open source calculator and it can be downloaded freely from this page. An Excel sheet and a Google sheet are included, if you don’t want to use the Python script. If you use FL Mobile, you can load the Python script into a Python app such as QPython.
Click the button below to download the Window executable, the Python source code and the Excel/Google sheets from GitHub.