  Given a set of unit-disks in the plane with union area $A$, what fraction of
$A$ can be covered by selecting a pairwise disjoint subset of the disks? Rado
conjectured 1/4 and proved $1/4.41$. Motivated by the problem of
channel-assignment for wireless access points, in which use of 3 channels is a
standard practice, we consider a variant where the selected subset of disks
must be 3-colourable with disks of the same colour pairwise-disjoint. For this
variant of the problem, we conjecture that it is always possible to cover at
least $1/1.41$ of the union area and prove $1/2.09$. We also provide an
$O(n^2)$ algorithm to select a subset achieving a $1/2.77$ bound.
