Mana fixing in a Cube
Not at all.

A quick Gatherer Search revealed at least 25 non-Green, fairly inexpensive basic land searchers (most $0.10 commons). Key cards of note:


The Panoramas: Example Bant Panorama, Naya Panorama
Terminal Moraine, Evolving Wilds, Terramorphic Expanse, Ghost Quarter, Oath of Lieges
Artifact Searchers - Armillary Sphere et. Al.
Basic Landcyclers 


This is without even listing all the dual lands that are available. There is a thread on the Multiplayer Wizards forum that displays alternatives to the original duals for people on a budget. The top post of the thread breaks the dual/tri lands into categories, first by cost, then by cycle.

Finally, there are also artifacts that tap for any color, or three color(Obelisk of Esper, Obelisk of Naya), or cheap Signet cycle (Boros Signet,  Azorius Signet, et. al.).