I am making some add-in to PowerPoint.
I would like to let user choose color using colordialog (or some other this kind control). But it would be the best if it would look exactly like built-in color dialog/color picker in PowerPoint, and with the same colors in sections Theme Colors, Custom Colors and Standard Colors. Is it achievable? If yes, how can I achieve it?
It really depends on what you need to use the color for. Office has many pre-defined controls that can be easily incorporated into an addin, some of which use the standard Office color picker (which includes the theme colors, custom colors, etc. that you are looking for). You can download a list of all Office controls from the Microsoft website (you will only need to use the PowerPointControls.xlsx file). Any of the controls listed in the file can be added to your addin by specifying the idMso in the ribbon XML (assuming you are creating a ribbon). You will need to look through all of the controls to se if there is one that matches the functionality you are looking for.
Note that most of the controls have some sort of additional functionality attached to them in addition to selecting a color. I have not yet found one that selects and returns a color. Hopefully what ever functionality you are in need of is included in one of the controls. You may be able to get a better answer if you provide more information on your specific application.