Can you target a creature you control that has shroud with your own spells?

Shroud is defined in CR 702.18a: a permanent or player with shroud cannot be the target of spells or abilities. Crucially, this applies to any spell or ability, regardless of who controls it — your own included.

This is different from Hexproof (CR 702.11a), which only prevents targeting by opponents. If you want to buff, enchant, or otherwise target one of your own creatures, you want it to have Hexproof, not Shroud.

So if your creature has Shroud, you cannot attach an Aura to it, you cannot target it with pump spells like Giant Growth, and you cannot target it with your own activated abilities. The protection is absolute and symmetrical.

Concrete example: You control a Morphling (which has Shroud in some printings) and you cast Giant Growth. You cannot legally choose Morphling as the target for Giant Growth, even though you control it. You'd need a different creature to target, or the spell simply cannot be cast if Morphling is your only creature.

Remember: if you want a creature that only your opponents can't target, look for Hexproof instead. Shroud protects from everyone, including you.