Context :

Aims : By using the full span of multicolor data on a representative sample of first overtone RR Lyrae stars in the Large Magellanic Cloud ( LMC ) we revisit the problem of the incidence rate of the amplitude/phase-modulated ( Blazhko ) stars .

Methods : Multicolor data , obtained by the MAssive Compact Halo Objects ( MACHO ) project , are utilized through a periodogram averaging method .

Results : The method of analysis enabled us to increase the number of detected multiperiodic variables by 18 % relative to the number obtained by the analysis of the best single color data .
We also test the maximum modulation period detectable in the present dataset .
We find that variables showing amplitude/phase modulations with periods close to the total time span can still be clearly separated from the class of stars showing period changes .
This larger limit on the modulation period , the more efficient data analysis and the longer time span lead to a substantial increase in the incidence rate of the Blazhko stars in comparison with earlier results .
We find altogether 99 first overtone Blazhko stars in the full sample of 1332 stars , implying an incidence rate of 7.5 % .
Although this rate is nearly twice of the one derived earlier , it is still significantly lower than that of the fundamental mode stars in the LMC .
The by-products of the analysis ( e.g. , star-by-star comments , distribution functions of various quantities ) are also presented .

Conclusions :