Yes, you can pay with M-PESA!
To do so, you must link your M-PESA account to your PayPal account.
If you do not yet have a PayPal account, you can create one for free here: PayPal Mobile Money Service with M-PESA
Transfer money from your M-PESA account into your PayPal account, then login to your USA Green Card account.
Select the PayPal payment option to complete your payment.