Officially Honda recommends that you use a IRC GP-21FZ (3.00-21 51P) for the front and a IRC GP-22R (120/80-18M/C 62P) for the rear. But I guess that is exactly what is now on the Honda CRF250L...
The 21” front and 18” rear wheel limits your tire choices a bit. Of course for off-road riding the combination of 21” and 18” wheels give you enormous choice, but for street riding I only know of one tire.
The Continental ContiTrail ATTACK which is an excellent tire for road riding, they're standard mounted on the BMW R1200GS.
The only downside is that the Continental ContiTrail ATTACK is not available in 120/80-18, they have the 140/80-18 (which is a bit wider) but I'm not sure if it will fit...
Anyway, the Bangkok Continental motorcycle tire dealer can help you with that.... call them 02-224-2490 (probably in Thai for best result).
Attached you can also see the profile of the ContiTrail ATTACK tire