Enamel Paint Stain Removal from Clothing.
You should be able to remove the paint stain by rubbing the area with liquid dishwashing detergent, let stand a few minutes, then wash. If the stain is persistent, you can spray the stain with Easy-Off oven cleaner, let set for about 30 minutes, then launder. Test this on a non-visible area first to check for color fastness in your pants. I would recommend washing the pants in cold or warm water, as hot water will cause them to fade and wear faster.

Note: Paint or varnish are usually rather difficult to remove. If the stain is taken when fresh it may usually be removed by dissolving with turpentine or gasoline. Either of these treatments will dissolve the oil and the colored matter can be brushed out when dry. After a paint stain has become thoroughly dry it is very difficult to remove and probably should be undertaken only by a professional.

Latex Paint Removal from Clothing.  Rubbing alcohol dissolves latex paint. Just wipe it away. For dried latex paint, let it soak in alcohol a little, or rub with an alcohol-soaked Q-Tip, then wipe the paint away.  In the laundry, wet the spot with alcohol, lift the paint spot manually or put it in the washer when it has dissolved.