Jno's link is for Windows 10. (It's probably much the same for Windows 7). If you're using Windows 11, here's the method to use:
Click the 'Start' icon.
Select 'Settings'
In some versions of Windows 11, you'll see 'Accessibility' in the left-hand panel. If so, click on it.
If 'Accessibility' isn't in that location, click the 'hamburger' (three horizontal lines) at the top of the window and then select 'Accessibility' from there.
Select 'Mouse Pointer & Touch'.
Select the colour you want for your mouse pointer. (Clicking on the yellow one allows you to choose from a range of colours.
Drag the 'Size' slider to the right. As you do so, the size of the pointer that you're dragging with will change, so that you can see what each setting will look like.
When you've achieved the result that you're looking for, simply close the window to confirm your actions.